tools/import.lua: fix 'flagged' table name

Created by: myhro

Hi,

An error was occurring when running the import script with config.db.init = true:

Function: update_flagged
Database error: no such table: flagged
SQL Query:
        UPDATE flagged SET updated = strftime('%s', 'now')
        WHERE repo = :repo
        AND origin = :origin
        AND version = :version

luajit: tools/import.lua:416: attempt to index local 'stmt' (a nil value)
stack traceback:
        tools/import.lua:416: in function 'update_flagged'
        tools/import.lua:463: in main chunk
        [C]: at 0x55a63415fc6e

Changing it from flagged.flagged to flagged fixed it.

Regards, Tiago.