avutil/tests/color_utils: reduce accuracy threshold to pass to 1e-7

Fixes FATE on a variety of configurations due to accuracy problems in
floating point math. Most constants tested against here are not even
specified with 7 decimal digits.

Reviewed-by: Niklas Haas <git@haasn.dev>

libavutil/tests/color_utils.c

@@ -70,7 +70,7 @@ int main(int argc, char *argv[])
             printf("trc=%s calling func(%f) expected=%f roundtrip=%f\n",
                     name, test_data[i], result, roundtrip);
 
-            if (result > 0.0 && fabs(roundtrip - test_data[i]) > 1e-8) {
+            if (result > 0.0 && fabs(roundtrip - test_data[i]) > 1e-7) {
                 printf("  FAIL\n");
                 return 1;
             }