Revert "[mlir] Add a postprocessing parameter in Pattern"

This reverts commit 02596693.
This reverts commit 3c5b4dab.

The build is broken:

mlir/test/lib/Dialect/Test/TestOps.td:988:7: error: Value specified for template argument 'Pat:supplemental_results' is of type dag; expected type list<dag>: (addBenefit 10)
def : Pat<(OpD $input), (OpF $input), [], (addBenefit 10)>;
      ^