scripted-diff: Replace CCriticalSection with RecursiveMutex

Summary:
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1. Delete outdated alias for RecursiveMutex sed -i -e '/CCriticalSection/d' ./src/sync.h
2. Replace use of outdated alias with RecursiveMutex sed -i -e 's/CCriticalSection/RecursiveMutex/g' $(git grep -l CCriticalSection)

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This is a backport of Core PR17891

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D5825