Python: Add change-note

python/ql/src/change-notes/2023-08-29-fixed-jsonify-xss-fp.md

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+category: minorAnalysis
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+* Improved _Reflected server-side cross-site scripting_ (`py/reflective-xss`) query to not alert on data passed to `flask.jsonify`. Since these HTTP responses are returned with mime-type `application/json`, they do not pose a security risk for XSS.