BTS_Tests/DTX: remove redundant RSL channel number check

We never launch this test case in DTX mode on anything else than
TCH/F, so it does not make sense to check this all the time.

Change-Id: I6e971d87f26253f4283c47b7f8826d14a2567a9b
Related: OS#4801
diff --git a/bts/BTS_Tests.ttcn b/bts/BTS_Tests.ttcn
index 1a659a2..735a36a 100644
--- a/bts/BTS_Tests.ttcn
+++ b/bts/BTS_Tests.ttcn
@@ -6743,12 +6743,6 @@
 		}
 
 		if (dtxd) {
-			if (not match(g_chan_nr, t_RslChanNr_Bm(?))) {
-				T.stop;
-				f_rsl_chan_deact();
-				f_L1CTL_DM_REL_REQ(L1CTL, g_chan_nr);
-				Misc_Helpers.f_shutdown(__BFILE__, __LINE__, fail, "Received fill frame on non-TCH/F channel; DTX is only allowed on TCH/F!");
-			}
 			if (fn > first_fn + frame_dtx_tchf_mod) {
 				T.stop;
 				f_rsl_chan_deact();