x11-toolkits/rubygem-gdk4: Update to 4.2.6

Changes:	https://github.com/ruby-gnome/ruby-gnome/releases
		https://github.com/ruby-gnome/ruby-gnome/blob/main/NEWS.md

x11-toolkits/rubygem-gdk4/Makefile

 PORTNAME=	gdk4
-PORTVERSION=	4.2.5
+PORTVERSION=	4.2.6
 CATEGORIES=	x11-toolkits rubygems
 MASTER_SITES=	RG
 

x11-toolkits/rubygem-gdk4/distinfo

-TIMESTAMP = 1735228218
-SHA256 (rubygem/gdk4-4.2.5.gem) = 54cc0b86d255363c05e1d3c7b843dfb70186f0523bb2f323222d3da7fc52d62f
-SIZE (rubygem/gdk4-4.2.5.gem) = 30720
+TIMESTAMP = 1738090204
+SHA256 (rubygem/gdk4-4.2.6.gem) = b7640e351c87989e9b9a025d10e68d4bee74fe1aa37505d09753701da0483dae
+SIZE (rubygem/gdk4-4.2.6.gem) = 30720