refactor: remove check_length in the error message of unbalanced system

src/systems/abstractsystem.jl

@@ -2219,13 +2219,13 @@ function check_eqs_u0(eqs, dvs, u0; check_length = true, kwargs...)
     if u0 !== nothing
         if check_length
             if !(length(eqs) == length(dvs) == length(u0))
-                throw(ArgumentError("Equations ($(length(eqs))), unknowns ($(length(dvs))), and initial conditions ($(length(u0))) are of different lengths. To allow a different number of equations than unknowns use kwarg check_length=false."))
+                throw(ArgumentError("Equations ($(length(eqs))), unknowns ($(length(dvs))), and initial conditions ($(length(u0))) are of different lengths."))
             end
         elseif length(dvs) != length(u0)
             throw(ArgumentError("Unknowns ($(length(dvs))) and initial conditions ($(length(u0))) are of different lengths."))
         end
     elseif check_length && (length(eqs) != length(dvs))
-        throw(ArgumentError("Equations ($(length(eqs))) and Unknowns ($(length(dvs))) are of different lengths. To allow these to differ use kwarg check_length=false."))
+        throw(ArgumentError("Equations ($(length(eqs))) and Unknowns ($(length(dvs))) are of different lengths."))
     end
     return nothing
 end