fix(python): regard pair children as data sources

[elsapet]

Description

To handle mongodb cases of NoSQLi such as

collection.find_one({"username": <some user input> })

Prior to this suggested fix, pattern is not catching on pair values as data sources

(dictionary (pair key: (_) @key value: (_) @value) @pair) @root

Checklist

If this is your first time contributing please sign the CLA

• I've added test coverage that shows my fix or feature works as expected.
• I've updated or added documentation if required.