Fix default sky process mode not being Real-Time

The change in 09563e4bd8fa4dda8802b3b48f111f3c1de499d8 wasn't
consistently carried out everywhere needed.

servers/rendering/renderer_rd/renderer_scene_sky_rd.h

@@ -254,7 +254,7 @@ public:
 
 		int radiance_size = 256;
 
-		RS::SkyMode mode = RS::SKY_MODE_AUTOMATIC;
+		RS::SkyMode mode = RS::SKY_MODE_REALTIME;
 
 		ReflectionData reflection;
 		bool dirty = false;