[Radius] Make dictionary.starent.vsa1 the default dictionary.
at least with the trace in Bug 10688 that makes the most sense.

Change-Id: I76213449076a2f49a4b72c6dd87b022fb10b9eef
Reviewed-on: https://code.wireshark.org/review/5242
Reviewed-by: Anders Broman <a.broman58@gmail.com>