Update pull_request.yml

Let's run the CI workflow on main branch.

Author: AlexITC

.github/workflows/pull_request.yml

@@ -2,9 +2,9 @@ name: Build the app
 
 on:
   push:
-    branches: [ master ]
+    branches: [ main ]
   pull_request:
-    branches: [ master ]
+    branches: [ main ]
 
 concurrency:
   # Only run once for latest commit per ref and cancel other (previous) runs.
@@ -36,4 +36,4 @@ jobs:
         run: CI=true sbt +compile
 
       - name: Run tests
-        run: CI=true sbt +test
+        run: CI=true sbt +test