build: don't run test workflow on doc dir on macOS

Leaving it in the Linux workflow because addons tests are affected by
changes to addons.md example code. So we need to keep that running
somewhere for docs changes, but one platform seems sufficient.

PR-URL: #37999
Reviewed-By: Rich Trott <rtrott@gmail.com>

.github/workflows/test-macos.yml

@@ -8,6 +8,8 @@ on:
       - canary
       - v[0-9]+.x-staging
       - v[0-9]+.x
+    paths-ignore:
+      - 'doc/**'
 
 env:
   PYTHON_VERSION: 3.9