docs: update apmschema url to use apm-data

apm schema was moved to apm-data a long time ago and the apm-server files are just a mirror

update the script to use apm-data files to we can stop mirroring them in apm-server

Author: kruskall

spec/support/match_json_schema_matcher.rb

@@ -21,7 +21,7 @@
 require 'json-schema'
 require 'open-uri'
 
-base = 'https://raw.githubusercontent.com/elastic/apm-server/master/docs/spec/v2'
+base = 'https://raw.githubusercontent.com/elastic/apm-data/main/input/elasticapm/docs/spec/v2'
 
 SCHEMA_URLS = {
   metadatas: "#{base}/metadata.json",