Remove bogus entries in gist point_ops operator class.

These entries could never be matched to an index clause because they don't
have the index datatype on the left-hand side of the operator.  (Their
commutators are in the opclass, which is sensible, but that doesn't mean
these operators should be.)  Spotted by a test that I recently added to
opr_sanity to catch exactly this type of thinko.  AFAICT there is no code
in gistproc.c that is specifically meant to cover these cases, so nothing
to remove at that level.