tests: Remove variable-length lookbehind tests for GRegex

PCRE2 10.43 has now introduced support for variable-length lookbehind, so these tests now fail if GLib is built against PCRE2 10.43 or higher.

See https://github.com/PCRE2Project/pcre2/blob/e8db6fa7137f4c6f66cb87e0a3c9467252ec1ef7/ChangeLog#L94.

Rather than making the tests conditional on the version of PCRE2 in use, just remove them. They are mostly testing the PCRE2 code rather than any code in GLib, so don’t have much value.

This should fix CI runs on msys2-mingw32, which updated to PCRE2 10.43 2 days ago.

Signed-off-by: Philip Withnall pwithnall@gnome.org