Reduce unnecessary job redundancy

Quoting the docs:
"If multiple triggering events for your workflow occur at the same time,
multiple workflow runs will be triggered."

Author: michaelosthege

.github/workflows/pipeline.yml

@@ -1,6 +1,6 @@
 name: pipeline
 
-on: [push, pull_request]
+on: [push]
 
 jobs:
   test-dotnet: