Per #23148, we now call set_custom_default_matcher within proxy_startup.py in order to preserve backwards compatibility and ignore headers that we now omit from recordings. Eventually, once recordings are free from these headers, we should remove this call and use the default matcher upon startup.

Note: at this point, we should also revert any set_custom_default_matcher calls that set bodiless matching to set_bodiless_matcher. The linked PR has details about this change as well.