backends/x11: fix colormap leak

Vlad Zahorodniirequested to merge
work/cherry-pick-1747518f into Plasma/6.2

If we change the backend the colormap will get leak, the colormap should be released with xcb_free_colormap before the window destoryed.

Signed-off-by: Chaojiang Luo luochaojiang@uniontech.com

(cherry picked from commit 1747518f)

Co-authored-by: Chaojiang Luo luochaojiang@uniontech.com

Merge request reports