Fixed another URL for ballot reconciliation.

Author: GinoCanessa

xml/FHIR-subscriptions-backport.xml

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <specification 
   gitUrl="https://github.com/HL7/fhir-subscription-backport-ig"
-  url="http://hl7.org/fhir/uv/subscriptions-backport-ig"
+  url="http://hl7.org/fhir/uv/subscriptions-backport"
   ciUrl="http://build.fhir.org/ig/HL7/fhir-subscription-backport-ig"
   ballotUrl="http://hl7.org/fhir/uv/subscriptions-backport/2021Jan"
   defaultWorkgroup="fhir-i"