Use continue on error for -next jobs

~~Apparently github's automerge is based on the job's properties not
the branch protection rules.~~ From what I gather, seems to make the
overall job succeed even if a specific run fails. This is exactly what
we want.

After checking again the selection was such a pain in the ass I got
one of the status checks wrong in the ruleset, and selected one of the
pypy-3.11 jobs as required. Even after `continue-on-error`-ing and the
overall check now passing the branch still doesn't merge.
`continue-on-error` seems like it's useful regardless, for better
reporting, so leaving it.

.github/workflows/ci.yml

@@ -71,6 +71,7 @@ jobs:
   test:
     runs-on: ubuntu-latest
     needs: compile
+    continue-on-error: ${{ matrix.python-version == '3.13' || matrix.python-version == 'pypy-3.11' }}
     strategy:
       fail-fast: false
       matrix: