[skip ci] Fix golint warning of log (#9994)

Signed-off-by: dragondriver <jiquan.long@zilliz.com>

internal/log/log.go

@@ -140,6 +140,7 @@ func S() *zap.SugaredLogger {
 	return _globalS.Load().(*zap.SugaredLogger)
 }
 
+// R returns utils.ReconfigurableRateLimiter.
 func R() *utils.ReconfigurableRateLimiter {
 	return _globalR.Load().(*utils.ReconfigurableRateLimiter)
 }