Drop wrong vty cfg line ms-power-control

Those two BTS backends never had their own MS Power Control Loop, so
they should be using the "osmo" common one. This wrong value "dsp" used
to be accepted for no good reason, but it's no longer the case. Let's
remove the line to let the backend take the default one (osmo).

Change-Id: I842fce2b8185c53d1684747afcfc3ae8fba1afee

src/osmo_gsm_tester/templates/osmo-bts-octphy.cfg.tmpl

@@ -49,6 +49,5 @@ bts 0
   power-ramp max-initial 23000 mdBm
   power-ramp step-size 2000 mdB
   power-ramp step-interval 1
-  ms-power-control dsp
   phy ${trx.phy_idx} instance ${trx.instance_idx}
 %endfor

src/osmo_gsm_tester/templates/osmo-bts-virtual.cfg.tmpl

@@ -44,5 +44,4 @@ bts 0
   power-ramp max-initial 23000 mdBm
   power-ramp step-size 2000 mdB
   power-ramp step-interval 1
-  ms-power-control dsp
   phy 0 instance 0