Deleted component templates that are no longer used

no issue

- we had a few template files left over where their backing JS files had been deleted

ghost/admin/app/components/gh-mobiledoc.hbs

@@ -1 +0,0 @@
-{{yield}}

ghost/admin/app/components/gh-modal-dialog.hbs

@@ -1,18 +0,0 @@
-<div class="modal-container js-modal-container" {{action "closeModal"}}>
-    <article class="{{klass}} js-modal">
-        <section class="modal-content" {{action "noBubble" bubbles=false preventDefault=false}}>
-            {{#if title}}<header class="modal-header"><h1>{{title}}</h1></header>{{/if}}
-            {{#if showClose}}<a class="close" href="" title="Close" {{action "closeModal"}}>{{svg-jar "close"}}<span class="hidden">Close</span></a>{{/if}}
-            <section class="modal-body">
-                {{yield}}
-            </section>
-            {{#if confirm}}
-            <footer class="modal-footer">
-                {{! Buttons must be on one line to prevent white-space errors }}
-                <button type="button" class="{{rejectButtonClass}} btn-minor" {{action "confirm" "reject"}} data-test-modal-reject-button>{{confirm.reject.text}}</button><button type="button" class="{{acceptButtonClass}}" {{action "confirm" "accept"}} data-test-modal-accept-button>{{confirm.accept.text}}</button>
-            </footer>
-            {{/if}}
-        </section>
-    </article>
-</div>
-<div class="modal-background js-modal-background"></div>

ghost/admin/app/components/gh-tags-management-container.hbs

@@ -1 +0,0 @@
-{{yield this}}

ghost/admin/app/components/modal-billing.hbs

@@ -1,7 +0,0 @@
-<div class="gh-billing-close">
-    <button class="close" href title="Close" {{on "click" (action "closeModal")}}>
-        {{svg-jar "close"}}
-    </button>
-</div>
-
-<GhBillingIframe></GhBillingIframe>