[bug] Remove dependency graph plugin

It fails reporting, and actions suggested in
https://github.com/marketplace/actions/sbt-dependency-submission#unexpected-status-403
don't work and are also not particularly safe.

.github/workflows/ci-scala.yaml

@@ -3,7 +3,7 @@ name: Scala CI
 on:
   push:
     branches: [ "main" ]
-  pull_request:
+  pull_request: {}
   workflow_dispatch: {}
 
 permissions:
@@ -24,6 +24,3 @@ jobs:
         cache: 'sbt'
     - name: Run tests
       run: sbt test
-      # Optional: This step uploads information to the GitHub dependency graph and unblocking Dependabot alerts for the repository
-    - name: Upload dependency graph
-      uses: scalacenter/sbt-dependency-submission@ab086b50c947c9774b70f39fc7f6e20ca2706c91