Fixes a bug where Series.iloc assignment incorrectly converted dictionary values to Series objects when the target Series had dtype="object". This issue occurred due to improper handling in the Copy-on-Write (CoW) implementation.

Fixes a bug where Series.iloc assignment incorrectly converted dictionary values to Series objects when the target Series had dtype="object". This issue occurred due to improper handling in the Copy-on-Write (CoW) implementation. #5937