fix(config): reduced preprocessing replicas from 2 to 1 (#6181)

Discussed with Anya - we said it looks like the replicas for Loculus
preprocessing should be one instead of two.

### PR Checklist
- [ ] All necessary documentation has been adapted.
- [ ] The implemented feature is covered by appropriate, automated
tests.
- [ ] Any manual testing that has been done is documented (i.e. what
exactly was tested?)

🚀 Preview: Add `preview` label to enable

Author: tombch

kubernetes/loculus/values.yaml

@@ -1403,7 +1403,7 @@ defaultOrganismConfig: &defaultOrganismConfig
       image: ghcr.io/loculus-project/preprocessing-nextclade
       args:
         - "prepro"
-      replicas: 2
+      replicas: 1
       configFile: &preprocessingConfigFile
         log_level: DEBUG
         batch_size: 100