fix(oiiotool): handle reset() return in set_colorconfig

OIIO_NODISCARD_ERROR added to ColorConfig::reset() in color.h requires
updating set_colorconfig to use the return value.

Replaced the has_error() check with a direct check of bool return from reset().

Signed-off-by: Luna Kim <177369799+luna-y-kim@users.noreply.github.com>

Author: luna-y-kim

src/oiiotool/oiiotool.cpp

@@ -2325,8 +2325,7 @@ static void
 set_colorconfig(Oiiotool& ot, cspan<const char*> argv)
 {
     OIIO_DASSERT(argv.size() == 2);
-    ot.colorconfig().reset(argv[1]);
-    if (ot.colorconfig().has_error()) {
+    if (!ot.colorconfig().reset(argv[1])) {
         ot.errorfmt("--colorconfig", "{}", ot.colorconfig().geterror());
     }
 }