ci(renovate): Incease MR Limits

This patch increases the amount of MRs that can be open at the
same time, to improve batch updates, given the growing number
of software deployed by this repository.

renovate.json

@@ -6,7 +6,7 @@
     ":prHourlyLimitNone",
     "regexManagers:dockerfileVersions"
   ],
-  "prConcurrentLimit": 10,
+  "prConcurrentLimit": 20,
   "semanticCommits": "enabled",
   "flux": {
     "fileMatch": ["\\.yaml$"]