fix: linter issue

megacheck, gosimple and unused has been deprecated and subsumed by
staticcheck. And staticcheck also has been upgraded. we need to update
code for the linter issue.

close: #2945

Signed-off-by: Wei Fu <fuweid89@gmail.com>

content/local/locks.go

@@ -47,7 +47,5 @@ func unlock(ref string) {
 	locksMu.Lock()
 	defer locksMu.Unlock()
 
-	if _, ok := locks[ref]; ok {
-		delete(locks, ref)
-	}
+	delete(locks, ref)
 }