fix(docs): _time_format=sqlite corresponds to format 4

Since _time_format=sqlite was introduced in 064df839 it has used (as described in that commit message):

the time package format "2006-01-02 15:04:05.999999999-07:00". This is the format mattn/go-sqlite3 uses and is format 4 at https://sqlite.org/lang_datefunc.html#time_values.

A couple months later this parameter was documented in 8e27ffc8 as corresponding to format 7 which is not and has never been the case (format 7 has a T between the date and the time).