Fix #125228: Image Editor Memory leaks showing image tooltip thumbnail

Looks like a simple oversight in 8937c0bcab

To resolve, just free the `ImBuf` (same as done in other places that use
`uiTooltipImage`)

Pull Request: https://projects.blender.org/blender/blender/pulls/125231

source/blender/editors/interface/regions/interface_region_tooltip.cc

@@ -1624,6 +1624,7 @@ static void ui_tooltip_from_image(Image &ima, uiTooltipData &data)
     UI_tooltip_text_field_add(&data, {}, {}, UI_TIP_STYLE_SPACER, UI_TIP_LC_NORMAL);
     UI_tooltip_text_field_add(&data, {}, {}, UI_TIP_STYLE_SPACER, UI_TIP_LC_NORMAL);
     UI_tooltip_image_field_add(&data, image_data);
+    IMB_freeImBuf(ibuf);
   }
 }