Update link to jinja2 extensions doc

[ClausHolbechArista]

Change Summary

Update link to jinja2 extensions doc

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Code style update (formatting, renaming)
• Refactoring (no functional changes)
• Documentation content changes
• Other (please describe):

Related Issue(s)

CI failing because mkdocs verifications complain.

Component(s) name

arista.avd

Proposed changes

Change link from https://svn.python.org/projects/external/Jinja-2.1.1/docs/_build/html/extensions.html to https://jinja.palletsprojects.com/extensions/

How to test

CI should pass.

Checklist:

• My code has been rebased from devel before I start
• I have read the CONTRIBUTING document.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have updated molecule CI testing accordingly
• All new and existing tests passed (pre-commit, make linting and make sanity-lint).

[titom73]

LGTM!