[mlir] drop unnecssary transform.with_pdl_patterns from tests, NFC

Many tests wrap the piece of the IR related to the transform dialect
into `transform.with_pdl_patterns` without actually using PDL patterns
inside. Some of these are leftovers from migration to `structured.match`
and some others are cargo cult, both are useless and pollute the tests.

Reviewed By: guraypp

Differential Revision: https://reviews.llvm.org/D135661