download_dump: Add -revision parameter
download_dump: Add -revision parameter

Add `-revision` parameter in
`scripts/maintenance/download_dump.py` which used for
specifying the revision of the file dump that wanna be
downloaded.

Bug: T183789
Change-Id: I3e7e22f3f5f35e71e3793f8f5b568c7e97aa4b1c

magul/pywikibot-core,magul/pywikibot-core,wikimedia/pywikibot-core,wikimedia/pywikibot-core,PersianWikipedia/pywikibot-core