Allow GAL_DRAWING_CONTEXT dtor to throw exceptions.

These destructors are implicitly noexcept, which woudnt't allow
OpenGL errors to be caught in DoRePaint.

Fixes https://gitlab.com/kicad/code/kicad/issues/12117

include/gal/graphics_abstraction_layer.h

@@ -1112,7 +1112,7 @@ public:
         m_gal->BeginDrawing();
     }
 
-    ~GAL_DRAWING_CONTEXT()
+    ~GAL_DRAWING_CONTEXT() noexcept( false )
     {
         m_gal->EndDrawing();
     }