Deprecate / Remove pandas.util.testing.assert_raises_regex #29187
Description
As noted by @simonjayhawkins in #29174 (comment) we have some assert_raises_regex code laying around in pandas.util.testing that isn't used internally. Can rip out a chunk of code if we get rid of that.
I think we need to deprecate as pandas.util.testing is part of the leaky API, though removal is an option as well.