pantheon: more build fixes by using older vala
pantheon: more build fixes by using older vala

An extension of commit b49e798763.  /cc PR #92592.
I expect it's "safer" when whole pantheon uses the same version.
Fixes build of wingpanel-indicator-session; maybe some others, too.
Now I built whole pantheon attrset and tests.pantheon.x86_64-linux

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs