st/icon-theme: Remove unnecessary CLAMP()

The ClutterColor struct members are 8-bit unsigned integers, so
they are always in the 0 to 255 range.

Spotted by coverity.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2679>

src/st/st-icon-theme.c

@@ -3659,9 +3659,9 @@ static char *
 color_to_string_noalpha (const ClutterColor *color)
 {
   return g_strdup_printf ("rgb(%d,%d,%d)",
-                          CLAMP (color->red, 0, 255),
+                          color->red,
-                          CLAMP (color->green, 0, 255),
+                          color->green,
-                          CLAMP (color->blue, 0, 255));
+                          color->blue);
 }
 
 static void