ci: update Alpine-based builds to Alpine 3.23

Alpine 3.23 was released three days ago. See
<https://www.alpinelinux.org/posts/Alpine-3.23.0-released.html>.

Author: striezel

.github/workflows/alpine.yml

@@ -5,7 +5,7 @@ on: push
 jobs:
   alpine:
     runs-on: ubuntu-24.04
-    container: 'alpine:3.22'
+    container: 'alpine:3.23'
     steps:
       # Git is required so that actions/checkout does a proper Git checkout.
       - name: Install Git in container

.github/workflows/alpine_arm.yml

@@ -6,7 +6,7 @@ jobs:
   alpine:
     runs-on: ubuntu-24.04-arm
     container:
-      image: 'alpine:3.22'
+      image: 'alpine:3.23'
       # Volume needed for monkey-patch step.
       volumes:
         - /:/host
@@ -27,13 +27,12 @@ jobs:
           apk add nodejs
           sed -i 's~ID=alpine~ID=nopine~g' /etc/os-release
           cd /host/home/runner/actions-runner/*/externals/
+          # Fake Node.js 20 for older actions.
+          # Currently, Alpine 3.23 has Node.js 24.11.1.
           rm -rf node20/*
           mkdir node20/bin
           ln -s /usr/bin/node node20/bin/node
-          # Fake Node.js 24 for actions/checkout@v6.
-          # Currently, Alpine 3.22 has Node.js 22.16.0, but that seems to work,
-          # too, because it looks like checkout is not using any stuff specific
-          # to Node.js 24.
+          # "Fake" Node.js 24 for actions/checkout@v6.
           rm -rf node24/*
           mkdir node24/bin
           ln -s /usr/bin/node node24/bin/node