ci: Fix publishing of documentation on push (#657)

Enable `nox-cross-arch` test for push events because if we don't do
this, the `publish-docs` will not run on pushes, so the in-development
documentation will not be published.

While cross-arch tests are generally executed in the merge queue on the
identical commit, activating them for push events provides an added
layer of security. This is especially important in scenarios where
emergency pushes might bypass the merge queue.

Author: llucax

.github/workflows/ci.yaml

@@ -81,7 +81,7 @@ jobs:
 
   nox-cross-arch:
     name: Cross-arch tests with nox
-    if: github.event_name == 'merge_group'
+    if: github.event_name != 'pull_request'
     strategy:
       fail-fast: false
       # Before adding new items to this matrix, make sure that a dockerfile
@@ -185,7 +185,7 @@ jobs:
     runs-on: ubuntu-20.04
     steps:
       - name: Return true
-        run: true
+        run: "true"
 
 
   build: