ci: disable concurrency-limits lint (#15371)

Disable this new lint from zizmor, the cure is worse than the disease.

Background of the check:
https://docs.zizmor.sh/audits/#concurrency-limits

Setting concurrency-limits will e.g. fail previous in-progress builds
for the same branch/PR, including `main`. Such "cancelled" builds
display and notify exactly as failures, when they really aren't. This
can cause a lot of noise and confusion!

Given that maintainers must approve before actions are run from a new
contributor, it doesn't seem like the best tradeoff to scan for this
rule and cancel (fail) such builds. Better to ensure all workflows have
timeouts better than the default (6h), if we want to prevent waste of
actions minutes.

Author: rmuir

.github/zizmor.yml

@@ -0,0 +1,5 @@
+---
+rules:
+  # Setting these limits causes failed builds which can be confusing
+  concurrency-limits:
+    disable: true