add markdown file extension

ruby/ql/lib/change-notes/2022-10-20-expand-faraday-model-for-ssrf-sink.md

@@ -2,4 +2,4 @@
 category: minorAnalysis
 ---
 
-- Instantiations using `Faraday::Connection.new` are now recognized as part of `FaradayHttpRequest`s, meaning they will be considered as sinks for queries such as `rb/request-forgery`.
+- Instantiations using `Faraday::Connection.new` are now recognized as part of `FaradayHttpRequest`s, meaning they will be considered as sinks for queries such as `rb/request-forgery`.