remove version check and 9s const after v1.27 release

[jsoref]

• in Delete Namespace: fix incompatible change in reclaim resources workflow #7385, @alexshtin added:
  

  temporal/service/worker/deletenamespace/reclaimresources/workflow.go

  Lines 156 to 157 in ab20b73

  	// TODO: remove version check and 9s const after v1.27 release.
  	namespaceCacheRefreshDelay := 9 * time.Second

https://github.com/temporalio/temporal/releases/tag/v1.27.0 was released 11 months ago.
https://github.com/temporalio/temporal/releases/tag/v1.28.0 was released in June
https://github.com/temporalio/temporal/releases/tag/v1.29.0 was released in October