Update command for generating TRX report (#3917)

* Update command for generating TRX report

Previous command results in:

```
Option '--report-trx-filename' has invalid arguments:
file name argument must not contain path (e.g. --report-trx-filename myreport.trx)
```

* Fix command

Author: kbegiedza

docs/docs/extensions/extensions.md

@@ -108,7 +108,7 @@ Run your tests with the `--report-trx` flag:
 dotnet run --configuration Release --report-trx
 
 # Specify output location
-dotnet run --configuration Release --report-trx --report-trx-filename ./reports/testresults.trx
+dotnet run --configuration Release --results-directory ./reports --report-trx --report-trx-filename testresults.trx
 ```
 
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