ci: skip validate workflow on ARM64 runners

The hassfest and HACS validator actions both depend on amd64-only
Docker images (ghcr.io/home-assistant/hassfest, hacs/action). On
ARM64 runners — like the Gitea Actions instance hosting this fork —
those images pull but fail with "exec format error" because no
multi-arch image is published.

Validation still runs on GitHub's amd64 ubuntu-latest runners, where
it actually matters for HACS distribution.

.github/workflows/validate.yml

@@ -16,6 +16,7 @@ jobs:
   hassfest:
     name: Hassfest validation
     runs-on: ubuntu-latest
+    if: runner.arch != 'ARM64'
     steps:
       - uses: actions/checkout@v4
       - uses: home-assistant/actions/hassfest@master
@@ -23,6 +24,7 @@ jobs:
   hacs:
     name: HACS validation
     runs-on: ubuntu-latest
+    if: runner.arch != 'ARM64'
     steps:
       - uses: actions/checkout@v4
       - uses: hacs/action@main