Update docs

update reference of opn to open

docs/readme.md

@@ -58,7 +58,7 @@ Note that some flag functionality is only available to the CLI. The set of share
 | `chromeFlags` | Ignored, Chrome is not launched for you. |
 | `outputPath` | Ignored, output is returned as string in `.report` property. |
 | `saveAssets` | Ignored, artifacts are returned in `.artifacts` property. |
-| `view` | Ignored, use the `opn` npm module if you want this functionality. |
+| `view` | Ignored, use the `open` npm module if you want this functionality. |
 | `enableErrorReporting` | Ignored, error reporting is always disabled for node. |
 | `listAllAudits` | Ignored, not relevant in programmatic use. |
 | `listTraceCategories` | Ignored, not relevant in programmatic use. |