adjust workflow to only run on either "push to master" or PR

Otherwise for a PR from a branch of the archunit repo itself this will trigger duplicate builds, since both events trigger.

Signed-off-by: Peter Gafert <[email protected]>

Author: codecholeric

.github/workflows/build.yml

@@ -1,6 +1,10 @@
 name: CI
 
-on: [push, pull_request]
+on:
+  push:
+    branches:
+      - master
+  pull_request:
 
 jobs:
   build:

.github/workflows/gradle-wrapper-validation.yml

@@ -1,5 +1,10 @@
 name: "Validate Gradle Wrapper"
-on: [push, pull_request]
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
 
 jobs:
   validation: