[docs] Use double quotes over single quotes for match stmt grammar

[Fidget-Spinner]

The Python Language Reference uses " over ' for denoting keywords, and this section uses ' to denote soft keywords. This patch just fixes the grammar to be consistent with the rest of the language reference.

[Fidget-Spinner]

It currently looks like this here:
https://docs.python.org/3.10/reference/compound_stmts.html#the-match-statement
The other patterns follow the same convention.

I think this is skip news and skip issue. This was something I did halfway in the original pattern matching docs PR, but forgot to apply to everything.