Revert "Add valgrind suppressions for wcsrtombs optimizations"

Revert "Add valgrind suppressions for wcsrtombs optimizations"

This reverts commit bf070ce09e05943d6484de0ec17c7b02f2690a6d.

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