Update MAVSDK instantiation to new V2 API across documentation

[KarthiAru]

• Updated MAVSDK instantiation to comply with V2 API changes across the following documentation files: missions.md, connections.md, follow_me.md, telemetry.md, offboard.md, taking_off_landing.md.
• Replaced old instantiation Mavsdk mavsdk; with the new instantiation Mavsdk mavsdk{Mavsdk::Configuration{Mavsdk::ComponentType::GroundStation}};.
• The Mavsdk class now requires a configuration to be passed as a constructor argument to specify the component type.
• Ensured all examples reflect the updated instantiation method for consistency and accuracy.