vty: remove groundless statement about filler type 'dummy'

Dummy bursts have nothing to do with A5/x encryption, and I see
no reason why (and how?!?) would using that filler type break
encryption in osmo-bts-trx.  I asked the author of this code
back in August 2020 [1], and so far didn't get any response.

[1] https://lists.osmocom.org/pipermail/openbsc/2020-August/013208.html

Change-Id: Iae513d7acbb8ef682e1744ac8726cbd6ece8bd87
diff --git a/CommonLibs/trx_vty.c b/CommonLibs/trx_vty.c
index adce897..4e265b6 100644
--- a/CommonLibs/trx_vty.c
+++ b/CommonLibs/trx_vty.c
@@ -333,8 +333,7 @@
 	"Filler burst settings\n"
 	"Filler burst type (default=zero)\n"
 	"Send an empty burst when there is nothing to send (default)\n"
-	"Send a dummy burst when there is nothing to send on C0 (TRX0) and empty burst on other channels."
-	" Use for OpenBTS compatibility only, don't use with OsmoBTS as it breaks encryption.\n"
+	"Send a dummy burst when there is nothing to send on C0 (TRX0) and empty burst on other channels.\n"
 	"Send a GMSK modulated Normal Burst with random bits when there is nothing to send."
 	" Use for spectrum mask testing. Configure 'filler tsc' to set training sequence.\n"
 	"Send an 8-PSK modulated Normal Burst with random bits when there is nothing to send."