Match keyword argument name elision syntax to whatever is adopted in Python

[evhub]

Current Coconut syntax: https://coconut.readthedocs.io/en/latest/DOCS.html#keyword-argument-name-elision

Discussion of possible new Python syntax: https://discuss.python.org/t/syntactic-sugar-to-encourage-use-of-named-arguments/36217/131

Coconut syntax should be deprecated in favor of whatever Python adopts.

[evhub]

PEP: https://peps.python.org/pep-0736/

~Though I'm going to wait on this until there's a final verdict here; I like Coconut's syntax better, so if the PEP is rejected then we'll just stick with the current syntax.~

[evhub]

The old syntax has been deprecated in favor of the PEP 736 one as of coconut-develop>=3.1.0-post_dev10.