Fix: Slow USD import with certain OpenColorIO configs

As evidenced by #138868, checking all colorspaces to see if they are sRGB
can be very slow, due to loading all LUTs into memory. Instead use a simpler
check by a list of names only, which is still better than the hardcoded
single name used in Blender 4.4.

Ideally recent configs will use the ColorInterop Forum alias so we can
find the sRGB colorspace reliably.

source/blender/imbuf/intern/colormanagement.cc

@@ -1195,13 +1195,6 @@ bool IMB_colormanagement_space_name_is_srgb(const char *name)
 
 const char *IMB_colormanagement_srgb_colorspace_name_get()
 {
-  for (const int colorspace_index : blender::IndexRange(g_config->get_num_color_spaces())) {
-    const ColorSpace *colorspace = g_config->get_color_space_by_index(colorspace_index);
-    if (colorspace->is_srgb()) {
-      return colorspace->name().c_str();
-    }
-  }
-
   /* Make a best effort to find by common names. First two are from the ColorInterop forum. */
   const char *names[] = {"sRGB Encoded Rec.709 (sRGB)",
                          "srgb_rec709_scene",