bpo-42755: Fix sqlite3.Connection.backup docs (GH-23965)

bpo-42755: Fix sqlite3.Connection.backup docs (GH-23965) · python/cpython@abba83b

Original file line number	Diff line number	Diff line change
`@@ -546,7 +546,7 @@ Connection Objects`
`546`	`546`	`con.close()`
`547`	`547`
`548`	`548`
`549`		`- .. method:: backup(target, *, pages=0, progress=None, name="main", sleep=0.250)`
	`549`	`+ .. method:: backup(target, *, pages=-1, progress=None, name="main", sleep=0.250)`
`550`	`550`
`551`	`551`	`This method makes a backup of a SQLite database even while it's being accessed`
`552`	`552`	`by other clients, or concurrently by the same connection. The copy will be`