Fixed linter error

ghost/admin/.lint-todo

@@ -1189,3 +1189,4 @@ add|ember-template-lint|no-passed-in-event-handlers|39|24|39|24|2692530760cb1f71
 add|ember-template-lint|no-passed-in-event-handlers|58|24|58|24|ce0d7e2e732b22ce3643fb9b1ac6ecef07c275ff|1646697600000|1649286000000|1651878000000|app/templates/setup.hbs
 add|ember-template-lint|no-passed-in-event-handlers|77|24|77|24|80681fcec2258c3d81a231bbd635aa1f03ff1452|1646697600000|1649286000000|1651878000000|app/templates/setup.hbs
 add|ember-template-lint|no-duplicate-landmark-elements|16|16|16|16|1661d2edb187b634c8187e5ecb0db15a4c7262fc|1646697600000|1649286000000|1651878000000|app/templates/signin.hbs
+remove|ember-template-lint|style-concatenation|90|20|90|20|95c5634b86fb8d9deffe53d77bd746f8b62571a3|1646611200000|1649199600000|1651791600000|app/templates/signin.hbs

ghost/admin/.template-lintrc.js

@@ -3,7 +3,7 @@ module.exports = {
 
     rules: {
         'no-forbidden-elements': ['meta', 'html', 'script'],
-        'no-implicit-this': {allow: ['now', 'site-icon-style']},
+        'no-implicit-this': {allow: ['now', 'site-icon-style', 'accent-color-background']},
         'no-inline-styles': false
     }
 };

ghost/admin/app/controllers/signin.js

@@ -5,7 +5,7 @@ import $ from 'jquery';
 import Controller, {inject as controller} from '@ember/controller';
 import ValidationEngine from 'ghost-admin/mixins/validation-engine';
 import classic from 'ember-classic-decorator';
-import {action, computed} from '@ember/object';
+import {action} from '@ember/object';
 import {alias} from '@ember/object/computed';
 import {htmlSafe} from '@ember/template';
 import {isArray as isEmberArray} from '@ember/array';
@@ -42,12 +42,6 @@ export default class SigninController extends Controller.extend(ValidationEngine
     @alias('model')
         signin;
 
-    @computed('config.accent_color')
-    get accentColor() {
-        let color = this.get('config.accent_color');
-        return color;
-    }
-
     @action
     authenticate() {
         return this.validateAndAuthenticate.perform();

ghost/admin/app/controllers/signup.js

@@ -1,6 +1,5 @@
 import Controller from '@ember/controller';
 import {alias} from '@ember/object/computed';
-import {computed} from '@ember/object';
 import {get} from '@ember/object';
 import {isArray as isEmberArray} from '@ember/array';
 import {
@@ -22,11 +21,6 @@ export default Controller.extend({
 
     signupDetails: alias('model'),
 
-    accentColor: computed('config.accent_color', function () {
-        let color = this.get('config.accent_color');
-        return color;
-    }),
-
     actions: {
         validate(property) {
             return this.signupDetails.validate({property});

ghost/admin/app/helpers/accent-color-background.js

@@ -0,0 +1,14 @@
+import Helper from '@ember/component/helper';
+import classic from 'ember-classic-decorator';
+import {htmlSafe} from '@ember/template';
+import {inject as service} from '@ember/service';
+
+@classic
+export default class AccentColorBackgroundHelper extends Helper {
+    @service config;
+
+    compute() {
+        const color = this.get('config.accent_color');
+        return htmlSafe(`background: ${color};`);
+    }
+}

ghost/admin/app/templates/signin.hbs

@@ -80,7 +80,7 @@
                     @class="login gh-btn gh-btn-login gh-btn-block gh-btn-icon js-login-button"
                     @type="submit"
                     @tabindex="3"
-                    style="background: {{this.accentColor}};" />
+                    style={{accent-color-background}} />
             </form>
 
             <p class="main-error">{{if this.flowErrors this.flowErrors}}&nbsp;</p>

ghost/admin/app/templates/signup.hbs

@@ -69,7 +69,7 @@
                 </GhFormGroup>
 
                 <GhTaskButton @buttonText="Create Account &rarr;" @type="submit" @form="signup" @defaultClick={{true}} @runningText="Creating"
-                    @task={{this.signup}} @data-test-button="signup" @class="gh-btn gh-btn-signup gh-btn-block gh-btn-icon" @tabindex="3" style="background: {{this.accentColor}};" />
+                    @task={{this.signup}} @data-test-button="signup" @class="gh-btn gh-btn-signup gh-btn-block gh-btn-icon" @tabindex="3" style={{accent-color-background}} />
             </form>
             {{#if this.flowErrors}}
                 <p class="main-error">{{this.flowErrors}}&nbsp;</p>