doc: minor modification

Author: franckgaga

src/controller/execute.jl

@@ -488,7 +488,7 @@ Call `periodsleep(mpc.estim.model)`.
 periodsleep(mpc::PredictiveController, busywait=false) = periodsleep(mpc.estim.model, busywait)
 
 """
-    setstate!(mpc::PredictiveController, x̂, P̂=nothing) -> mpc
+    setstate!(mpc::PredictiveController, x̂[, P̂]) -> mpc
 
 Call [`setstate!`](@ref) on `mpc.estim` [`StateEstimator`](@ref).
 """

src/estimator/execute.jl

@@ -330,7 +330,7 @@ function validate_args(estim::StateEstimator, ym, d, u=nothing)
 end
 
 """
-    setstate!(estim::StateEstimator, x̂, P̂=nothing) -> estim
+    setstate!(estim::StateEstimator, x̂[, P̂]) -> estim
 
 Set `estim.x̂0` to `x̂ - estim.x̂op` from the argument `x̂`, and `estim.P̂` to `P̂` if applicable.