linux/x11: Remove x11_gl_context_destroy function

This function is never called and the logic already exists in the x11_window_destroy function

core/linux-dist/x11.cpp

@@ -570,12 +570,6 @@ void x11_window_set_text(const char* text)
 	}
 }
 
-void x11_gl_context_destroy()
-{
-	glXMakeCurrent((Display*)x11_disp, None, NULL);
-	glXDestroyContext((Display*)x11_disp, (GLXContext)x11_glc);
-}
-
 void x11_window_destroy()
 {
 	destroy_empty_cursor();