Update TestRazorCompiledItem.cs (dotnet#54211)

Author: WeihanLi

src/Mvc/shared/Mvc.Views.TestCommon/TestRazorCompiledItem.cs

@@ -47,12 +47,12 @@ public TestRazorCompiledItem(Type type, string kind, string identifier, object[]
     public static string GetChecksum(string content)
     {
         var bytes = SHA1.HashData(Encoding.UTF8.GetBytes(content));
-        return Convert.ToHexString(bytes).ToLowerInvariant();
+        return Convert.ToHexStringLower(bytes);
     }
 
     public static string GetChecksumSHA256(string content)
     {
         var bytes = SHA256.HashData(Encoding.UTF8.GetBytes(content));
-        return Convert.ToHexString(bytes).ToLowerInvariant();
+        return Convert.ToHexStringLower(bytes);
     }
 }