Update to python 3.8 for docs build process

[FileMagic]

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[FileMagic]

This was causing circle-ci to fail on docs build for the version of pip used within st2 core was not available for docs building.

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This can be seen here: https://app.circleci.com/pipelines/github/StackStorm/st2docs/699/workflows/7bd58acc-1d9e-4ec2-8a9c-b6749d701f44/jobs/3441

[FileMagic]

It seems that @nzlosh pinned the version of jinja2 due to a bug with sphinx upstream to fix this same issue in the past with the build error from https://app.circleci.com/pipelines/github/StackStorm/st2docs/701/workflows/3c124ade-5cad-4b0c-a056-aa6662fb6a94/jobs/3443. I am guessing I am going to have to see if a newer version of sphinx can be used for this, however, I think I am going to do this after working through the updates for python 3.10 for I don't know what that will do once I bump to 3.10 for building these pages.

[FileMagic]

It seems that @nzlosh pinned the version of jinja2 due to a bug with sphinx upstream to fix this same issue in the past with the build error from https://app.circleci.com/pipelines/github/StackStorm/st2docs/701/workflows/3c124ade-5cad-4b0c-a056-aa6662fb6a94/jobs/3443. I am guessing I am going to have to see if a newer version of sphinx can be used for this, however, I think I am going to do this after working through the updates for python 3.10 for I don't know what that will do once I bump to 3.10 for building these pages.

That pin occured in 40ae03c