ci: use GHA ARM runners for image build

Signed-off-by: Aurora Gaffney <[email protected]>

Author: agaffney

.github/workflows/ci-docker.yml

@@ -51,7 +51,7 @@ jobs:
           mv /tmp/.buildx-cache-new /tmp/.buildx-cache
 
   build-arm64:
-    runs-on: ["self-hosted", "ARM64"]
+    runs-on: ubuntu-24.04-arm
     steps:
       - uses: actions/checkout@v4
       - name: qemu

.github/workflows/publish.yml

@@ -79,7 +79,7 @@ jobs:
           done
 
   build-arm64:
-    runs-on: ["self-hosted", "ARM64"]
+    runs-on: ubuntu-24.04-arm
     permissions:
       contents: read
       packages: write