CI: update image from ubuntu-20.04 to ubuntu-24.04

The ubuntu-20.04 image is now unsupported

Author: strub

.github/workflows/ci.yml

@@ -14,7 +14,7 @@ env:
 jobs:
   compile-opam:
     name: EasyCrypt compilation (opam)
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04
     container:
       image: ghcr.io/easycrypt/ec-build-box
     steps:
@@ -30,7 +30,7 @@ jobs:
     name: EasyCrypt compilation (nix)
     env:
       HOME: /home/runner
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04
     steps:
     - uses: actions/checkout@v4
     - name: Setup Nix
@@ -49,7 +49,7 @@ jobs:
   check:
     name: Check EasyCrypt Libraries
     needs: compile-opam
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04
     container:
       image: ghcr.io/easycrypt/ec-build-box
     strategy:
@@ -82,7 +82,7 @@ jobs:
 
   fetch-external-matrix:
     name: Fetch EasyCrypt External Projects Matrix
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04
     outputs:
       matrix: ${{ steps.set-matrix.outputs.matrix }}
     steps:
@@ -97,7 +97,7 @@ jobs:
   external:
     name: Check EasyCrypt External Projects
     needs: [compile-opam, fetch-external-matrix]
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04
     container:
       image: ghcr.io/easycrypt/ec-build-box
     strategy:
@@ -159,7 +159,7 @@ jobs:
     name: Check EasyCrypt External Projects (set-status)
     if: always()
     needs: [external]
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04
     steps:
     - uses: re-actors/alls-green@release/v1
       with:
@@ -172,7 +172,7 @@ jobs:
     if: |
       (github.event_name == 'push') ||
       (github.event_name == 'pull_request' && github.event.pull_request.head.repo.full_name == github.repository)
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04
     steps:
     - uses: technote-space/workflow-conclusion-action@v3
     - uses: zulip/github-actions-zulip/send-message@v1