Not existing URL at wiki to rad_eap_test

# Issue type
- Old URL at https://wiki.freeradius.org/guide/EAP-Clients#rad_eap_test 
***
## How to resolve the issue

An old link to source code:
```text
http://www.eduroam.cz/rad_eap_test/
```

replace with:
```text
https://github.com/CESNET/rad_eap_test/blob/master/rad_eap_test
```