sphinx: Fix the creation of the pre-commit file during the mr update

Change the default permission of the ~jenkins/.cache directory
created by the --mount option on the RUN command
It fixes all the following errors:
```
During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/jenkins/.local/bin/pre-commit", line 10, in <module>
    sys.exit(main())
  File "/home/jenkins/.local/lib/python3.7/site-packages/pre_commit/main.py", line 398, in main
    f'Command {args.command} failed to exit with a returncode',
  File "/usr/lib/python3.7/contextlib.py", line 130, in __exit__
    self.gen.throw(type, value, traceback)
  File "/home/jenkins/.local/lib/python3.7/site-packages/pre_commit/error_handler.py", line 73, in error_handler
    _log_and_exit(msg, ret_code, e, traceback.format_exc())
  File "/home/jenkins/.local/lib/python3.7/site-packages/pre_commit/error_handler.py", line 24, in _log_and_exit
    storedir = Store().directory
  File "/home/jenkins/.local/lib/python3.7/site-packages/pre_commit/store.py", line 52, in __init__
    os.makedirs(self.directory, exist_ok=True)
  File "/usr/lib/python3.7/os.py", line 221, in makedirs
    mkdir(name, mode)
PermissionError: [Errno 13] Permission denied: '/home/jenkins/.cache/pre-commit'
```

sphinx/Dockerfile

@@ -19,10 +19,13 @@ RUN --mount=type=cache,id=apt-cache,target=/var/cache/apt --mount=type=cache,id=
     plantuml \
     postgresql-autodoc \
     rsync \
-    tox
+    tox && \
+  mkdir /home/jenkins/.cache && \
+  chown jenkins:jenkins /home/jenkins/.cache
 
 USER jenkins
 
 RUN --mount=type=cache,id=pip-cache,target=/home/jenkins/.cache/pip,uid=115,gid=120 \
   python3 -m pip install --user --upgrade \
-    pre-commit
+    pre-commit \
+  && chown jenkins:jenkins /home/jenkins/.cache