Avoid running tests twice on PRs

Tests are triggered both on PRs as well as branch pushes, leading PRs to get double test runs. Only trigger the branch push on merge to master.

Author: carlpett

.github/workflows/test.yml

@@ -3,6 +3,8 @@ name: Tests
 on:
   pull_request:
   push:
+    branches:
+      - master
 
 env:
   GO_VERSION: '1.21'