Explicitly reference python2 in shebang for tncc-wrapper.py

The RPM build complains:
BUILDSTDERR: *** ERROR: ambiguous python shebang in /usr/libexec/openconnect/tncc-wrapper.py: #!/usr/bin/python. Change it to python3 (or python2) explicitly.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>

trojans/tncc-wrapper.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/python2
 
 # Lifted from Russ Dill's juniper-vpn-wrap.py, thus:
 #