Don't enforce Python 2 for utilities

The conv_gen.py utility was tested against both Python 2 and 3,
so there is no need to enforce Python 2. Also, having:

  #!/usr/local/bin/python{2|3}

is a bad idea, because Python may be installed in a different location.

Change-Id: I6007d481047b584db13d6eda70fb99f11f9ddaa1
diff --git a/src/gsm/Makefile.am b/src/gsm/Makefile.am
index 0439ce6..5387e3a 100644
--- a/src/gsm/Makefile.am
+++ b/src/gsm/Makefile.am
@@ -47,6 +47,6 @@
 
 # Convolutional codes generation
 gsm0503_conv.c: $(top_srcdir)/utils/conv_gen.py $(top_srcdir)/utils/conv_codes_gsm.py
-	$(AM_V_GEN)python2 $(top_srcdir)/utils/conv_gen.py gen_codes gsm
+	$(AM_V_GEN)python $(top_srcdir)/utils/conv_gen.py gen_codes gsm
 
 CLEANFILES = gsm0503_conv.c