ci: don't run Actions on non-master pushes

.github/workflows/build-tarball.yml

@@ -1,6 +1,10 @@
 name: Build from tarball
 
-on: [push, pull_request]
+on:
+  pull_request:
+  push:
+    branches:
+      - master
 
 env:
   FLAKY_TESTS: dontcare

.github/workflows/build-windows.yml

@@ -1,6 +1,10 @@
 name: build-windows
 
-on: [push, pull_request]
+on:
+  pull_request:
+  push:
+    branches:
+      - master
 
 env:
   PYTHON_VERSION: 3.8

.github/workflows/linters.yml

@@ -1,6 +1,10 @@
 name: linters
 
-on: [push, pull_request]
+on:
+  pull_request:
+  push:
+    branches:
+      - master
 
 env:
   PYTHON_VERSION: 3.8

.github/workflows/misc.yml

@@ -1,6 +1,10 @@
 name: misc
 
-on: [push, pull_request]
+on:
+  pull_request:
+  push:
+    branches:
+      - master
 
 env:
   NODE_VERSION: 12.x

.github/workflows/test-linux.yml

@@ -1,6 +1,10 @@
 name: test-linux
 
-on: [push, pull_request]
+on:
+  pull_request:
+  push:
+    branches:
+      - master
 
 env:
   PYTHON_VERSION: 3.8

.github/workflows/test-macos.yml

@@ -1,6 +1,10 @@
 name: test-macOS
 
-on: [push, pull_request]
+on:
+  pull_request:
+  push:
+    branches:
+      - master
 
 env:
   PYTHON_VERSION: 3.8