Clone the correct mongo branch based on the wiredtiger branch for many-collection-test

many-collection-test failed on Large scale tests

Host: ec2-3-89-186-1.compute-1.amazonaws.com
Project: WiredTiger (mongodb-5.0)
Commit: diff: WT-8422 Clear the on-disk cell time window if it is obsolete (#7214) (#7476)

Whenever we are rewriting an existing page image with the latest update of keys
on reconciliation, clear out any of the existing time windows from other keys
on the page, if they are obsolete.

Clearing the time window will decrease the size required to store the
same cell and also improves the performance.

(cherry picked from commit b757e1c61d3b2d54300d7b3be5b68f7316140fed)

Co-authored-by: Hari Babu Kommi <haribabu.kommi@mongodb.com> | 30 Jan 22 21:17 UTC
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