Avoid duplicate calculation of formattedSourceText

Co-Authored-By: Nsharwell <sam@tunnelvisionlabs.com>

src/Tools/dotnet-format/CodeFormatter.cs

@@ -166,7 +166,7 @@ private static async Task<Solution> FormatFilesInProjectAsync(ILogger logger, Pr
                         return null;
                     }
 
-                    return await formattedDocument.GetTextAsync(cancellationToken).ConfigureAwait(false);
+                     return formattedSourceText;
                 }, cancellationToken);
 
                 formattedDocuments.Add((documentId, formatTask));