Remove vestigial CHECK_FOR_INTERRUPTS call.

Commit e710b65c inserted code in md5_crypt_verify to disable and later
re-enable interrupts, with a CHECK_FOR_INTERRUPTS call as part of the
second step, to process any interrupts that had been held off.  Commit
6647248e removed the interrupt disable/re-enable code, but left behind
the CHECK_FOR_INTERRUPTS, even though this is now an entirely random,
pointless place for one.  md5_crypt_verify doesn't run long enough to
need such a check, and if it did, this would still be the wrong place
to put one.

src/backend/libpq/crypt.c

@@ -81,8 +81,6 @@ md5_crypt_verify(const Port *port, const char *role, char *client_pass,
 		return STATUS_ERROR;	/* empty password */
 	}
 
-	CHECK_FOR_INTERRUPTS();
-
 	/*
 	 * Compare with the encrypted or plain password depending on the
 	 * authentication method being used for this connection.  (We do not