Fix placement for comments within f-strings concatenations

[charliermarsh]

Summary

Restores the dangling comment handling for f-strings, which broke with the parenthesized expression code.

Closes #6898.

Test Plan

cargo test

No change in any of the similarity indexes or changed file counts:

project	similarity index	total files	changed files
cpython	0.76083	1789	1632
django	0.99957	2760	67
transformers	0.99927	2587	468
twine	0.99982	33	1
typeshed	0.99978	3496	2173
warehouse	0.99818	648	24
zulip	0.99942	1437	32

[charliermarsh]

\cc @davidszotten

[davidszotten]

note that black formats your first 3 examples differently (this may be due to existing/known differences)

(f"{1}" f"{2}")  # comment
(f"{1}" f"{2}")  # comment
(1, (f"{2}"))  # comment

[charliermarsh]

@davidszotten - Ah thank you for checking that! It does make sense to me since we tend to break on trailing comments unlike Black, so I don't think it needs to block here.