GHA: switch 3 more small jobs to ubuntu-slim

Follow-up to 30c49db6f7ad64c6819181283fd0baff44815441 #20431

Closes #20433

.github/workflows/checksrc.yml

@@ -32,7 +32,7 @@ permissions: {}
 jobs:
   checksrc:
     name: 'checksrc'
-    runs-on: ubuntu-24.04-arm
+    runs-on: ubuntu-slim
     steps:
       - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
         with:

.github/workflows/checkurls.yml

@@ -25,7 +25,7 @@ jobs:
   linkcheck:
     if: ${{ github.repository_owner == 'curl' || github.event_name != 'schedule' }}
     name: 'linkcheck'
-    runs-on: ubuntu-24.04-arm
+    runs-on: ubuntu-slim
     steps:
       - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
         with:

.github/workflows/distcheck.yml

@@ -209,7 +209,7 @@ jobs:
 
   missing-files:
     name: 'missing files'
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-slim
     timeout-minutes: 5
     needs: maketgz-and-verify-in-tree
     steps: