minor edit in rootpy browse script options

```
rootpy browse --help
usage: rootpy browse [-h] [-i] [-b] file [file ...]

positional arguments:
  file

optional arguments:
  -h, --help        show this help message and exit
  -i, --no-ipython  don't try to start ipython
  -b, --no-browser  don't try to start a browser
```