Fix --no-warning flag in README

Author: bokub

README.md

@@ -104,7 +104,7 @@ For anything more complicated, or for generating specs dynamically, you can also
 | `--wrapper`           | `-w`  | `declare namespace OpenAPI2` | How should this export the types?                                   |
 | `--output [location]` | `-o`  |           (stdout)           | Where should the output file be saved?                              |
 | `--camelcase`         | `-c`  |           `false`            | Convert `snake_case` properties to `camelCase`                      |
-| `--nowarning`         |       |           `false`            | Disables “autogenerated file” warning at the top of generated files |
+| `--no-warning`        |       |           `false`            | Disables “autogenerated file” warning at the top of generated files |
 | `--nowrapper`         | `-nw` |           `false`            | Disables rendering a wrapper                                        |
 
 ### Node