Changes

ttcn3-bts-test/osmo-bts.cfg: use default {fn,rts}-advance values

It's better if we run ttcn3-bts-test with the default values, given
that they were significantly reduced some time ago.

Change-Id: If8438adfdbc506d2b6b7858ea8a0ea859ba246a1
Related: I7da3d0948f38e12342fb714b29f8edc5e9d0933d (osmo-bts)
Related: OS#4487