Update the documentation

Flush no longer exists and is not actually required.

arm-datalake-store/filesystem/2016-11-01/swagger/filesystem.json

@@ -43,7 +43,7 @@
           "application/octet-stream"
         ],
         "operationId": "FileSystem_ConcurrentAppend",
-        "description": "Appends to the specified file. This method supports multiple concurrent appends to the file. NOTE: ConcurrentAppend and normal (serial) Append CANNOT be used interchangeably; once a file has been appended to using either of these append options, it can only be appended to using that append option. ConcurrentAppend DOES NOT guarantee order and can result in duplicated data landing in the target file. In order to close a file after using ConcurrentAppend, call the Flush method.",
+        "description": "Appends to the specified file. This method supports multiple concurrent appends to the file. NOTE: ConcurrentAppend and normal (serial) Append CANNOT be used interchangeably; once a file has been appended to using either of these append options, it can only be appended to using that append option. ConcurrentAppend DOES NOT guarantee order and can result in duplicated data landing in the target file.",
         "parameters": [
           {
             "name": "filePath",