sip_to_pjsip: Add cert_file.

When using the migration script sip_to_pjsip.py, cert_file was not migrated to
pjsip.conf. A previous change regarding this contained a copy/paste error.

ASTERISK-22374

Change-Id: I0fa72e9412117d53b4284fc6b83fa5b2b95ba03b

contrib/scripts/sip_to_pjsip/sip_to_pjsip.py

@@ -691,9 +691,9 @@ def set_tls_bindaddr(val, pjsip, nmapped):
     set_value('bind', bind, 'transport-tls', pjsip, nmapped, 'transport')
 
 
-def set_tls_cert_file(val, pjsip, section, nmapped):
+def set_tls_cert_file(val, pjsip, nmapped):
     """Sets cert_file based on sip.conf tlscertfile"""
-    set_value('cert_file', val, section, pjsip, nmapped,
+    set_value('cert_file', val, 'transport-tls', pjsip, nmapped,
               'transport')