vo_gpu: sync duplicated condition on peak computation

pass_color_map() (in video_shaders.c) and pass_colormanage() (video.c)
both duplicate the condition on whether to do peak computation. Peak
computation requires a compute shader, so if the duplicated conditions
don't match, video_shaders.c will generate a compute shader, but video.c
will try to run it as fragment shader. This leads to a "blue screen".

This can be reproduced by playing a HDTV video with --target-peak=99.

It's not clear how to fix this. Should pass_tone_map() be only invoked
if mp_trc_is_hdr() == true (what pass_colormanage() uses to decide
whether to enable peak computation), or should pass_colormanage() just
tell pass_color_map() to skip peak computation? Decide for the latter,
as it's more robust.

Even if not correct, at least it gets rid of the blue shit.

Fixes: #7149

video/out/gpu/video.c

@@ -2629,6 +2629,8 @@ static void pass_colormanage(struct gl_video *p, struct mp_colorspace src,
             "uint frame_max;"
             "uint counter;"
         );
+    } else {
+        tone_map.compute_peak = -1;
     }
 
     // Adapt from src to dst as necessary