ci(docs): Fix paths

.github/workflows/build-docs.yml

@@ -5,6 +5,8 @@ on:
     branches:
       - master
       - main
+    paths:
+      - docs/**
 permissions:
   contents: write
 jobs:
@@ -22,7 +24,7 @@ jobs:
         with:
           key: ${{ github.ref }}
           path: .cache
-      - run: pip install -r requirements.txt
+      - run: pip install -r docs/requirements.txt
       - run: mkdocs gh-deploy --force
         # Ref: https://github.com/ojacques/mkdocs-git-committers-plugin-2
         # Ref: https://github.com/ojacques/mkdocs-git-committers-plugin-2/issues/51#issuecomment-1951450239