gpu/internal/opengl: support sRGB emulation for desktop OpenGL

Desktop OpenGL implements a GL_FRAMEBUFFER_SRGB setting; query that instead
of the frambuffer color encoding.

With this change it is no longer necessary to enable FRAMEBUFFER_SRGB
in the macOS setup; remove it.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

app/internal/wm/gl_macos.m

@@ -84,5 +84,4 @@ void gio_prepareContext(void) {
 	GLuint defVBA;
 	glGenVertexArrays(1, &defVBA);
 	glBindVertexArray(defVBA);
-	glEnable(GL_FRAMEBUFFER_SRGB);
 }