[UnusedImport] Fix removing multiple uses

[jorgsowa]

Fixes removal of unused import for multiple uses.

Example of bug reported in another PR #6362 (comment)

namespace A;

use B, C;

echo B::class;

getrector.com/demo/755f134f-8f83-4bb1-a904-99ab62db0c6b

[samsonasik]

Thank you @jorgsowa, I will clear up variables usage in separate PR :)