add jedi-language-server 0.21.0

[bollwyvl]

Checklist

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Notes

• Pretty straight grayskull job
• the upstream only requires cached-property on 3.6/3.7, but it doesn't appear to harm anything testing with 3.9
• the hard jedi pin is rough, but given the issues we've had elsewhere in this area, I guess I'll take it!

[conda-forge-linter]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipes/jedi-language-server) and found it was in an excellent condition.

[bollwyvl]

@conda-forge/staged-recipes @conda-forge/help-python ready for review!

[bollwyvl]

Thanks!