ios_deployment_target = "11.0"

https://github.com/flutter/buildroot/blob/6b9d7c1c4bd0eeb176e0334b20f085d11e2f65bb/build/config/ios/ios_sdk.gni#L19

Other than rolling the buildroot into the engine in theory there shouldn't be any engine repo changes needed (see work done in flutter/engine#28743).

Blocked by #101960 and #101961.
(Seriously, I know the engine team is excited to do this, but please don't bump this until the tooling work is done or our users will get linker/build submission errors.)