storage: Enable PreVote by default.

Fixes #16950

Release note (performance improvement): Reduced disruption from nodes
recovering from network partitions.

pkg/storage/store.go

@@ -114,7 +114,7 @@ var storeSchedulerConcurrency = envutil.EnvOrDefaultInt(
 	"COCKROACH_SCHEDULER_CONCURRENCY", 8*runtime.NumCPU())
 
 var enablePreVote = envutil.EnvOrDefaultBool(
-	"COCKROACH_ENABLE_PREVOTE", false)
+	"COCKROACH_ENABLE_PREVOTE", true)
 
 var enableTickQuiesced = envutil.EnvOrDefaultBool(
 	"COCKROACH_ENABLE_TICK_QUIESCED", true)