doc: Update Action runner

Author: johanstokking

.github/workflows/pull_request.yml

@@ -5,7 +5,7 @@ on: pull_request
 jobs:
   build:
     name: Build docs
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04-4core
     steps:
       - name: Check out code
         uses: actions/checkout@v3

.github/workflows/release.yml

@@ -8,7 +8,7 @@ on:
 jobs:
   release:
     name: Release docs
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04-4core
     steps:
       - name: Check out code
         uses: actions/checkout@v3