CI: raise cross-run timeouts

On Ubuntu 22.04, these tests take significantly longer than they did on
20.04 for reasons not (yet) known.  In lieu of understanding, try
raising the timeouts.  We'd like to add `-j 2` as well, to take
advantage of both cores that the hosted runners offer, but that causes
its own failures (ctest receiving SIGTERM).

.github/workflows/main.yml

@@ -238,7 +238,7 @@ jobs:
     - name: Test
       working-directory: ${{github.workspace}}/build
       run: ctest --output-on-failure -E '(perf-.*)|(.*-malloc$)' --timeout 400
-      timeout-minutes: 30
+      timeout-minutes: 45
 
   windows:
     strategy: