gh-87260: Update sqlite3 signature docs to reflect actual implementation (GH-93840)

Align the docs for the following methods with the actual implementation:

- sqlite3.complete_statement()
- sqlite3.Connection.create_function()
- sqlite3.Connection.create_aggregate()
- sqlite3.Connection.set_progress_handler()
(cherry picked from commit d31834688bccb41fc136f780db83ffa12bef8cbd)

Co-authored-by: Erlend Egeberg Aasland <erlend.aasland@protonmail.com>