docs: fix SQLite tutorial CreateAuthor usage with RETURNING *

[Abhineshhh]

Summary

• The SQLite getting-started tutorial defines CreateAuthor as :one with RETURNING *, so sqlc generates (Author, error), not sql.Result.
• The Go example incorrectly treated the return value as sql.Result and called LastInsertId(), which does not compile.
• Update the example to use the returned Author (same pattern as the PostgreSQL tutorial) and compare full structs after GetAuthor.

Fixes #4468

Verification

1. Generated code from the tutorial schema.sql / query.sql with a local sqlc build:
   • CreateAuthor(ctx, CreateAuthorParams) (Author, error)
   • GetAuthor(ctx, id int64) (Author, error)
   • Author{ID int64; Name string; Bio sql.NullString}
2. Compiled and ran the fixed tutorial.go end-to-end with modernc.org/sqlite and an in-memory DB.
3. Program output included true from reflect.DeepEqual(insertedAuthor, fetchedAuthor).

Test plan

• Confirmed generated signatures match the fixed example
• go build and run of the full tutorial program succeeds
• Docs render as expected after merge

[Abhineshhh]

have a review @kyleconroy

[kyleconroy]

Thanks!