tree-sitter-c: update to 0.20.4.

Features

    add attribute_specifierto struct (4b6e0bc)
    rework release action (e17d0a1)

Bug Fixes

    rework typedef specifiers again (4c49fc3)
    swap precedences of assignnment and conditional expressions (f3559c6)
    disallow / after \S to better handle comments in preproc_arg (5890e77)
    make preproc newlines immediate so they don't span excess trailing newliens (41c0a15)

(wiz)