BUILD/MINOR: github: run the CI only on PRs

Author: mjuraga

.github/workflows/build.yml

@@ -1,5 +1,8 @@
 name: go build
-on: [push, pull_request]
+on:
+  pull_request:
+    branches:
+      - master
 jobs:
 
   build:

.github/workflows/check.yml

@@ -1,5 +1,8 @@
 name: Commit subject
-on: [pull_request]
+on:
+  pull_request:
+    branches:
+      - master
 jobs:
   check:
     runs-on: ubuntu-latest

.github/workflows/e2e.yml

@@ -1,5 +1,8 @@
 name: e2e
-on: [push, pull_request]
+on:
+  pull_request:
+    branches:
+      - master
 jobs:
   build:
     name: HAProxy

.github/workflows/lint.yml

@@ -1,5 +1,8 @@
 name: golangci-lint
-on: [push, pull_request]
+on:
+  pull_request:
+    branches:
+      - master
 jobs:
   golangci-lint:
     name: runner / golangci-lint
@@ -8,6 +11,6 @@ jobs:
       - name: Check out code into the Go module directory
         uses: actions/checkout@v1
       - name: golangci-lint
-        uses: reviewdog/action-golangci-lint@v1        
+        uses: reviewdog/action-golangci-lint@v1
         with:
           github_token: ${{ secrets.github_token }}