[ci,alt-arch] deactivate armv6 build

The builder fails for unknown reasons with illegal instruction.
Filed an upstream bug report at
https://github.com/uraimo/run-on-arch-action/issues/162 waiting for
a fix.

.github/workflows/alt-architectures.yml

@@ -13,8 +13,6 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - arch: armv6
-            distro: bookworm
           - arch: armv7
             distro: bookworm
           - arch: aarch64