api_changes: describe API changes with v0.33.0

[julianoes]

Goes with https://github.com/mavlink/MAVSDK/pull/694/.

[hamishwillee]

Modulo the comment looks great. The corresponding changes need to be made in the body of the docs as well

Minimally

• e.g. update to example https://mavsdk.mavlink.io/develop/en/examples/takeoff_and_land.html
• https://mavsdk.mavlink.io/develop/en/guide/connections.html

But every single doc shows how to get a system, and they might need to be modified.

[julianoes]

@hamishwillee thanks for the review! I'll go through the code examples and change them as well.

[julianoes]

@JonasVautherin updated as discussed.