Fix typo in `string.Join` (#50467)

Follow-up #44032.

diff --git a/src/libraries/System.Private.CoreLib/src/System/String.Manipulation.cs b/src/libraries/System.Private.CoreLib/src/System/String.Manipulation.cs
index 690c26a..efb7f5d 100644 (file)
--- a/src/libraries/System.Private.CoreLib/src/System/String.Manipulation.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/String.Manipulation.cs
@@ -578,9 +578,9 @@ namespace System
 
         public static string Join(string? separator, IEnumerable<string?> values)
         {
-            if (values is List<string?> valuesIList)
+            if (values is List<string?> valuesList)
             {
-                return JoinCore(separator.AsSpan(), CollectionsMarshal.AsSpan(valuesIList));
+                return JoinCore(separator.AsSpan(), CollectionsMarshal.AsSpan(valuesList));
             }
 
             if (values is string?[] valuesArray)