Remove temporary branches-file-location property in gradle.properties

This change cleans up the configuration by removing the property used for testing changes in BwC before the version field was introduced in branches.json. The associated TODO comment has also been removed.

Author: jozala

gradle.properties

@@ -22,7 +22,3 @@ org.gradle.java.installations.fromEnv=RUNTIME_JAVA_HOME
 
 # if configuration cache enabled then enable parallel support too
 org.gradle.configuration-cache.parallel=true
-
-# This is needed for testing changes in BwC before version field is introduced in branches.json on the main branch
-# TODO remove before merging to main
-org.elasticsearch.build.branches-file-location=https://raw.githubusercontent.com/jozala/elasticsearch/bwc-explicit-branches-version/branches.json