Remove broken _reprcompare disabling fixture in test_assertrewrite.py
Remove broken _reprcompare disabling fixture in test_assertrewrite.py

The `_pytest._code._reprcompare` that was referred to previously doesn't
exist -- it was moved to other places but wasn't updated. This regressed
in f423ce9c016aff0d84c4a68f6d972833d032181e. Now we don't want it
anymore, so keep the status quo by explicitly removing them.

nicoddemus/pytest,nicoddemus/pytest,markshao/pytest,The-Compiler/pytest,Akasurde/pytest,RonnyPfannschmidt/pytest,The-Compiler/pytest,pytest-dev/pytest