Revert "Add valgrind suppressions for wcsrtombs optimizations"

Revert "Add valgrind suppressions for wcsrtombs optimizations"

This reverts commit 71b2951ccc433a6dd799efedff9f5927c32440f6.

Per discussion, it's not desirable to add valgrind suppressions for
outside our own code base (e.g. glibc in this case), especially when
the suppressions may be platform-specific. There are better ways to
deal with that, e.g. by providing local suppressions.

Discussion: https://www.postgresql.org/message-id/flat/90ac0452-e907-e7a4-b3c8-15bd33780e62%402ndquadrant.com