feat: respect supplied versions in the nightly builds

Currently nightly containers only build main branches, ignoring the upstream triggers. Fixing that, would provide additional meaningful testing against main branches.

spack-environment/packages.yaml

@@ -158,7 +158,7 @@ packages:
     - '@2023-05-19'
   graphviz:
     require:
-    - '@8.0.1'
+    - '@12.1.0'
     - +expat +pangocairo
   hepmc3:
     require: