Merge pull request #3602 from crobibero/user-change-case

Fix username case change

(cherry picked from commit 8f11e057a2b3a2263d629ebcfbf29e54defe1666)
Signed-off-by: Joshua M. Boniface <joshua@boniface.me>

Jellyfin.Server.Implementations/Users/UserManager.cs

@@ -152,12 +152,12 @@ namespace Jellyfin.Server.Implementations.Users
                 throw new ArgumentException("Invalid username", nameof(newName));
             }
 
-            if (user.Username.Equals(newName, StringComparison.OrdinalIgnoreCase))
+            if (user.Username.Equals(newName, StringComparison.Ordinal))
             {
                 throw new ArgumentException("The new and old names must be different.");
             }
 
-            if (Users.Any(u => u.Id != user.Id && u.Username.Equals(newName, StringComparison.OrdinalIgnoreCase)))
+            if (Users.Any(u => u.Id != user.Id && u.Username.Equals(newName, StringComparison.Ordinal)))
             {
                 throw new ArgumentException(string.Format(
                     CultureInfo.InvariantCulture,