Docs: sqlite3 injection attack example is not an example of an SQL injection attack

[erlend-aasland]

The SQL injection attack example in the sqlite3 docs takes no user input, hence it is not susceptible to an injection attack and serves badly as an example.

Also, it does not mention injection attacks that exploit the load_extension SQL API.

• PR: gh-96250: Improve sqlite3 injection attack example #99270

• PR: [3.11] gh-96250: Improve sqlite3 injection attack example (GH-99270) #100119

• PR: [3.10] gh-96250: Improve sqlite3 injection attack example (GH-99270) #100120