Manually remove duplicated user operations in the old sequences.

[Wanderer777]

A couple of operation sequences that were recorded before the fix in 5423522e5f672270e13e33b1067098601244e3ec should be fixed manually. In particular, for participant cs-504 operations with timestamps 1307782748997 and 1307782749001 should be removed. And for participant cs-506 operations with timestamps 1308238981896, 1308238981899, 1308446718671, and 1308446718679 should be removed. See more details in issue #247.