Fix: freeze Jinja2 version

[ethanwharris]

What does this PR do?

Jinja2 just released a new version and caused an internal error in the docs build. Pinning the dependency to fix it.

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cc @Borda @rohitgr7

[Borda]

Is it only for PL or all other projects?

[tchaton]

LGTM !

[ethanwharris]

@Borda seems to be affecting everything. Same issue on Flash, I guess will hit TM too

[Borda]

@Borda seems to be affecting everything. Same issue on Flash, I guess will hit TM too

well thinking about really freezing all our docs requirements across projects as it is a specific task I do not expect that regular user would need building docs and if all these requirements are rather light... 🐰