Remove unused error in graceful manager (#29871)

As title.

(cherry picked from commit 1f0d31ce8fdfc8c32f84e4e0801c2d04b727bbd8)

modules/graceful/manager_unix.go

@@ -59,8 +59,8 @@ func (g *Manager) start() {
 	go func() {
 		defer func() {
 			close(startupDone)
-			// Close the unused listeners and ignore the error here there's not much we can do with it, they're logged in the CloseProvidedListeners function
-			_ = CloseProvidedListeners()
+			// Close the unused listeners
+			closeProvidedListeners()
 		}()
 		// Wait for all servers to be created
 		g.createServerCond.L.Lock()

modules/graceful/net_unix.go

@@ -129,25 +129,17 @@ func getProvidedFDs() (savedErr error) {
 	return savedErr
 }
 
-// CloseProvidedListeners closes all unused provided listeners.
-func CloseProvidedListeners() error {
+// closeProvidedListeners closes all unused provided listeners.
+func closeProvidedListeners() {
 	mutex.Lock()
 	defer mutex.Unlock()
-	var returnableError error
 	for _, l := range providedListeners {
 		err := l.Close()
 		if err != nil {
 			log.Error("Error in closing unused provided listener: %v", err)
-			if returnableError != nil {
-				returnableError = fmt.Errorf("%v & %w", returnableError, err)
-			} else {
-				returnableError = err
-			}
 		}
 	}
 	providedListeners = []net.Listener{}
-
-	return returnableError
 }
 
 // DefaultGetListener obtains a listener for the stream-oriented local network address: