Fix CI: install git in Arch container for update-pkgver

The runner now uses docker mode with archlinux:base-devel which
does not include git by default.

.gitea/workflows/update-pkgver.yaml

@@ -12,6 +12,9 @@ jobs:
   update-pkgver:
     runs-on: moonarch
     steps:
+      - name: Install dependencies
+        run: pacman -Sy --noconfirm git
+
       - name: Checkout source repo
         run: |
           git clone --bare http://gitea:3000/nevaforget/moonarch.git source.git