x11-toolkits/pango: update to 1.50.7

Changelog: https://gitlab.gnome.org/GNOME/pango/-/blob/1.50.7/NEWS

• coretext: Fix the build
• editing: Fix moving across paragraph boundaries in rtl
• layout: Try harder to survive without fonts
• Windows: Register a sans-serif font
• Windows: Try harder to load a font