It looks like `InConversionGroupFlags.UserDefinedReturnTypeAdjustment` is never actually used

It looks like we do not have a single unit-test that exercises a code path that uses ```InConversionGroupFlags.UserDefinedReturnTypeAdjustment```. We have code that is supposed to use it, but it appears that the code is not reachable in practice. We should either add proper test coverage, or remove the dead code and the flag in order to reduce complexity.

Start by locating InConversionGroupFlags.UserDefinedReturnTypeAdjustment and the code paths that are supposed to use it. Review existing unit-test coverage to determine whether the flag is reachable in practice. Done means either a test covers the reachable behavior or the dead code and flag are removed, based on the investigation.

Written by the indexing model from the issue text.