Consistent size/appearance of window-close-symbolic
Many GTK applications with CSDs use the window-*-symbolic icons for the CSD window decoration buttons. Breeze icons, however, use a smaller icon enclosed in a circle for the close button -- this is inconsistent with the rest of the Breeze window icons and the Breeze window decoration.
This commit fixes this inconsistency by using a larger, uncircled close button in window-close-symbolic.
Before:
After:
