CI: upgrade to opam 2.3.0, install from Ubuntu

The main issue is to drop Python 2.7 which has been removed from Ubuntu;
https://utcc.utoronto.ca/~cks/space/blog/python/Ubuntu2404PythonState

No need for manual binary downloads, since opam 2.3.0 is in Ubuntu 24.04:
https://opam.ocaml.org/doc/Install.html#Debian-and-Ubuntu

Signed-off-by: Daniel Maslowski <info@orangecms.org>

Author: orangecms

.github/workflows/verify.yml

@@ -14,10 +14,8 @@ jobs:
       with:
         persist-credentials: false
         submodules: 'true'
-    - name: Install opam dependencies
-      run: sudo apt update -y && sudo apt install -y pkg-config git rsync tar unzip m4 time curl ocaml build-essential bubblewrap gawk libgmp-dev python2.7 python3 python3-distutils libmpfr-dev
     - name: Install opam
-      run: curl "https://github.com/ocaml/opam/releases/download/2.1.5/opam-2.1.5-x86_64-linux" -Lo /usr/local/bin/opam && chmod +x /usr/local/bin/opam
+      run: sudo apt update && sudo apt install -y opam
     - name: Setup opam
       run: opam init -y
     - name: Setup opam switch