chore(gitpod): Pin python version to 3.11

Part-of: <https://dev.funkwhale.audio/funkwhale/funkwhale/-/merge_requests/2605>

.gitpod/Dockerfile

@@ -4,6 +4,8 @@ USER gitpod
 RUN sudo apt update -y \
     && sudo apt install libsasl2-dev libldap2-dev libssl-dev ffmpeg gettext -y
 
+RUN pyenv install 3.11 && pyenv global 3.11
+
 RUN pip install poetry pre-commit \
     && poetry config virtualenvs.create true \
     && poetry config virtualenvs.in-project true