.github: temporarily disable Infix Classic builds

Debugging build/runner problems with GitHub Actions.  Resolution pending
self-hosted runner becoming operational.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

.github/workflows/build.yml

@@ -13,7 +13,7 @@ jobs:
     strategy:
       matrix:
         platform: [aarch64, x86_64]
-        variant: [netconf, classic]
+        variant: [netconf]
       fail-fast: false
     steps:
       - uses: actions/checkout@v4