Remove query type `sql` from ballista protocol

[milenkovicm]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.

at the moment ballista protocol supports sending raw SQL to be executed

datafusion-ballista/ballista/core/proto/ballista.proto

Line 540 in 32f281a

string sql = 2 [deprecated=true]; // I'd suggest to remove this, if SQL needed use `flight-sql`

this has been deprecated for quite some time, maybe its time to be removed as it wont behave correctly

Describe the solution you'd like

Remove query type sql

Describe alternatives you've considered

Additional context

[mattcuento]

take