Use Python 3.8.10 for development of www-gitlab-com

Why is this change being made?

Python 3.8.2 has multiple security vulnerabilities including CVE-2021-23336, CVE-2021-3177, CVE-2020-27619, CVE-2020-14422, CVE-2020-26116, CVE-2019-20907, CVE-2020-8492, CVE-2019-18348 etc.

https://docs.python.org/release/3.8.10/whatsnew/changelog.html

Author Checklist

• Provided a concise title for the MR
• Added a description to this MR explaining the reasons for the proposed change, per say-why-not-just-what
• Assign this change to the correct DRI
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