tests: Do not run trust-pgp-4.scm

* tests/openpgp/Makefile.am (XTESTS): Remove test.
(EXTRA_DIST): Add test file.

There are two problems with this test: First a syntax error in the
file name so that the test was not used at all. Second the test
currently returns FAIL.

• Fixes-commit: c23a69970ba38edae9d3b2603825d18fbb732423
• Signed-off-by: Werner Koch <wk@gnupg.org>