ci: remove frontend-tests flow

These are no longer being used as much as they were, most of the stuff
it was hitting lives in separate repos now. Can be ripped out as such.

.github/workflows/frontend-test.yml

@@ -1,24 +0,0 @@
-name: frontend-test
-
-on:
-  pull_request:
-    paths:
-      - 'pkg/interface/**'
-      - 'pkg/btc-wallet/**'
-      - 'pkg/npm/**'
-
-jobs:
-  frontend-test:
-    runs-on: ubuntu-latest
-    name: "Test changed frontend packages"
-    steps:
-      - uses: actions/checkout@v2
-        with:
-          fetch-depth: 0
-      - run: git fetch --prune
-      - name: 'Setup root deps'
-        run: npm ci
-      - name: 'Setup dependencies'
-        run: npm run bootstrap
-      - name: 'Run tests'
-        run: npm run test -- --since origin/$GITHUB_BASE_REF  --include-dependents