[Discovery] MySQL 5.7 Clean Up in devstack

[UsamaSadiq]

Description

• This issue came up under the discusson on Nice-to-have Colima doc improvements #601
• MySQL 5.7 reached its end of life in Oct 2023 so it should be removed from devstack now.
• edx-platform has already stopped running migrations checks on MySQL 5.7 so we can start removing the support for MySQL 5.7 from devstack as well.

TODO

• arbi-bom team will be responsible of handling this clean up and assist the SRE team wherever needed.