Remove branch filter on PR triggers (#673 / #674)

This commit removes the branch filtering on PRs. It prevented the
build pipeline from triggering in certain cases but we want to
trigger it for all PRs, so the filtering just did not make sense.

Closes: #673
PR: #674

.github/workflows/build.yml

@@ -7,15 +7,14 @@ on:
   # We want to trigger our builds all the time for the default branch
   # except when Shipkit creates a new version tag
   push:
-    branches: 'main'
+    branches: ['main']
     tags-ignore:
       - 'v**'
   # Each pull request is important to us, doesn't matter from which branch.
   # Furthermore, we do not want to build on just the default GitHub Action
   # events, we also want to react onto `labeled` events for our extended
   # build execution
   pull_request:
-    branches: '*'
     types: [labeled, opened, synchronize, reopened]
   # We also utilize this pipeline for releasing. By providing a `version`
   # and setting `releasing` to `true`, we can trigger a release.