GitHub actions: don't run tests twice for github PRs

Author: schweikert

.github/workflows/test.yml

@@ -1,5 +1,10 @@
 name: Test
-on: [push, pull_request]
+on:
+  push:
+    branches:
+      - develop
+  pull_request:
+  workflow_dispatch:
 jobs:
   Test-Linux:
     runs-on: ${{ matrix.os }}