Fix gcc.dg/vect/bb-slp-46.c FAIL

When relaxing vectorization of possibly overflowing reductions I
failed to update a testcase that will now vectorize and no longer
test for what it was written for.  The following replaces the
vectorizable add with a division.

	* gcc.dg/vect/bb-slp-46.c: Use division instead of addition
	to avoid reduction vectorization.

gcc/testsuite/gcc.dg/vect/bb-slp-46.c

@@ -15,7 +15,7 @@ int foo ()
   a[1] = tem1;
   a[2] = tem2;
   a[3] = tem3;
-  return temx + temy;
+  return temx / temy;
 }
 
 /* We should extract the live lane from the vectorized add rather than