👷(CI) remove test-e2e-other-browser job

We don't maintain the test-e2e-other-browser job,
and it often fails due to various reasons.
To avoid unnecessary noise in our CI pipeline, we
will remove this job.

We are adding workflow_dispatch trigger to the e2e-tests
workflow, so that we can still run e2e tests on other
browsers when needed from the Github actions UI.

.github/workflows/impress-frontend.yml

@@ -73,14 +73,6 @@ jobs:
       projects: --project=chromium
       timeout-minutes: 25
 
-  test-e2e-other-browser:
-    needs: test-e2e-chromium
-    uses: ./.github/workflows/e2e-tests.yml
-    with:
-      browser-name: other-browser
-      projects: --project=firefox --project=webkit
-      timeout-minutes: 30
-
   bundle-size-check:
     runs-on: ubuntu-latest
     needs: install-dependencies