[3.11] gh-108843: fix ast.unparse for f-string with many quotes (#108980)

* [3.11] gh-108843: fix ast.unparse for f-string with many quotes

* 📜🤖 Added by blurb_it.

* simplify

---------

Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>