Remove ReplacePlaceHolders method

The private static method `ReplacePlaceHolders` was removed from `CreateEnvelopeCommandHandler.cs`. This method was used to replace placeholders in a string with values from a dictionary. Its removal indicates that this functionality is either no longer needed or has been refactored elsewhere in the codebase.

EnvelopeGenerator.Application/Envelopes/Commands/CreateEnvelopeCommandHandler.cs

@@ -607,12 +607,4 @@ public class CreateEnvelopeCommandHandler(IServiceProvider Provider, IMapper Map
             }
         }
     }
-
-    private static string ReplacePlaceHolders(string text, Dictionary<string, string> placeHolders)
-    {
-        foreach (var placeHolder in placeHolders)
-            text = text.Replace(placeHolder.Key, placeHolder.Value);
-
-        return text;
-    }
 }