gdk: Use correct parameter name to fix g-ir-scanner warning
../gdk/gdktoplevellayout.c:217: Warning: Gdk: gdk_toplevel_layout_get_maximized: unknown parameter 'maximized' in documentation comment, should be 'maximize'
../gdk/gdktoplevellayout.c:217: Warning: Gdk: gdk_toplevel_layout_get_maximized: unknown parameter 'maximized' in documentation comment, should be 'maximize'