community/vala-language-server: upgrade to 0.48.7
https://github.com/vala-lang/vala-language-server/releases/tag/0.48.6
( changelog for 0.48.7 is just 'fixed meson version' )
https://github.com/vala-lang/vala-language-server/releases/tag/0.48.6
( changelog for 0.48.7 is just 'fixed meson version' )