[X86] Remove unnecessary In64BitMode predicate from TEST64ri32. NFC

This appears to have been added when In64BitMode was added to a
bunch of instructions that don't have register operands. When an
instruction uses a register the parser will prevent a 64-bit
register from being parsed on a 32-bit target. But with only
memory and immediate operands this doesn't happen.

TEST64ri32 does have a register operand so the issue the predicate
was supposed to fix doesn't apply.