Fix #113323: Paint Secondary color not working in the Image Editor

Caused by c30d6571bb .

Above commit only updated the `BrushPainterCache` `invert` only when the
requirements for a float imbuf changed.
This however always needs to be updated.

Pull Request: https://projects.blender.org/blender/blender/pulls/113334

source/blender/editors/sculpt_paint/paint_image_2d.cc

@@ -164,11 +164,11 @@ static void brush_painter_2d_require_imbuf(
     cache->ibuf = nullptr;
     cache->tex_mask = nullptr;
     cache->lastdiameter = -1; /* force ibuf create in refresh */
-    cache->invert = invert;
   }
 
   cache->use_float = use_float;
   cache->use_color_correction = use_float && use_color_correction;
+  cache->invert = invert;
   cache->is_texbrush = (brush->mtex.tex && brush->imagepaint_tool == PAINT_TOOL_DRAW) ? true :
                                                                                         false;
   cache->is_maskbrush = (brush->mask_mtex.tex) ? true : false;