Remove recently added PL/Perl encoding tests

Remove recently added PL/Perl encoding tests

These only pass cleanly on UTF8 and SQL_ASCII encodings, besides the
Japanese encoding in which they were originally written, which is clearly
not good enough.  Since the functionality they test has not ever been
tested from PL/Perl, the best answer seems to be to remove the new tests
completely.

Per buildfarm results and ensuing discussion.