Revert "Add valgrind suppressions for wcsrtombs optimizations"

Revert "Add valgrind suppressions for wcsrtombs optimizations"

This reverts commit f57b94d9d0bbf42a18690d820f884dc0fc6bf79e.

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