workflows: don't test paths on `master`.

This avoids weirdness like the merged PR commits being pushed to scheduled opened PRs after merging.

It also avoids wasting resources.

.github/workflows/docker.yml

@@ -4,6 +4,8 @@ on:
     paths:
       - .github/workflows/docker.yml
       - Dockerfile
+    branches-ignore:
+      - master
   release:
     types:
       - published

.github/workflows/doctor.yml

@@ -8,6 +8,8 @@ on:
       - Library/Homebrew/extend/os/diagnostic.rb
       - Library/Homebrew/extend/os/mac/diagnostic.rb
       - Library/Homebrew/os/mac/xcode.rb
+    branches-ignore:
+      - master
 env:
   HOMEBREW_DEVELOPER: 1
   HOMEBREW_NO_AUTO_UPDATE: 1

.github/workflows/spdx.yml

@@ -3,6 +3,8 @@ on:
   push:
     paths:
       - .github/workflows/spdx.yml
+    branches-ignore:
+      - master
   schedule:
     - cron: '0 */12 * * *'
 jobs:

.github/workflows/tapioca.yml

@@ -3,6 +3,8 @@ on:
   push:
     paths:
       - .github/workflows/tapioca.yml
+    branches-ignore:
+      - master
   schedule:
     - cron: '0 */12 * * *'
 jobs: