[BasicAA] Ignore CanBeFreed in minimal extent reasoning

When determining NoAlias based on object size and dereferenceability
information, we can ignore frees for the same reason we can ignore
possible null pointers (if null is not a valid pointer): Actually
accessing the null pointer / freed pointer would be immediate UB,
and AA results are only valid under the assumption of an access.

This addresses a minor regression from D110745.

Differential Revision: https://reviews.llvm.org/D111028