Incorrect usage of PyUnicode_CompareWithASCIIString in suggestions.c

[pablogsal]

          It can only be used if the second argument is ASCII string. `item_str` is UTF-8 string. The behavior in such case is not defined.

Originally posted by @serhiy-storchaka in #27197 (comment)

Linked PRs

• gh-106025: Fix incorrect usage of PyUnicode_CompareWithASCIIString in suggestions.c #106026