Update click, mark mkdocs as not to be upgraded.

[kattni]

Click has finally posted an update that fixes the issue that was causing MkDocs live serve to fail.

literate-nav now has a warning stating that it's possible that MkDocs 2.0 may, without warning, replace the pip install mkdocs install. It seems unlikely to be a direct replacement for the current version. I have preemptively added a warning about now upgrading MkDocs, should this happen.

PR Checklist:

• All new features have been tested
• All new features have been documented
• I have read the CONTRIBUTING.md file
• I will abide by the code of conduct

[kattni]

This failure is happening on main as well. Looking into it.

[kattni]

There are two spots in every translation where the {% endif %} was missing. In sorting that out, I noticed that some of the tabbed content labels were translated; they are the same ones in every file, and it's not all of them. I have no idea why it's happening this way. I pushed the manual updates to the PO files so the locations of the issues were easy to communicate.

[freakboy3742]

As discussed in person yesterday, there's some rendering issues that seem to be related to translation of code blocks - but those were pre-existing. Landing this as is because it's clearly a fix for other problems (see beeware/beeware.github.io#766).