github/workflows: fix git safe.directory config

Signed-off-by: Koichi Shiraishi <zchee.io@gmail.com>

.github/workflows/gh-pages.yml

@@ -34,6 +34,7 @@ jobs:
         entrypoint: sh
         args: |
           -c \
-          "pip install -U --pre --compile --requirement /github/workspace/config/requirements.txt && \
+          "git config --global --add safe.directory /github/workspace && \
+           pip install -U --pre --compile --requirement /github/workspace/config/requirements.txt && \
            mkdocs build -c -f /github/workspace/config/mkdocs.yml && \
            mkdocs gh-deploy --config-file /github/workspace/config/mkdocs.yml --verbose --force"