This reverts commit d3bbc4b9.

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