Revert "Add valgrind suppressions for wcsrtombs optimizations"

Revert "Add valgrind suppressions for wcsrtombs optimizations"

This reverts commit 5b16a353543ecec36ffda68269defb7b1b002f60.

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