fix acausal tutorial

Author: ChrisRackauckas

Project.toml

@@ -1,7 +1,7 @@
 name = "ModelingToolkit"
 uuid = "961ee093-0014-501f-94e3-6117800e7a78"
 authors = ["Yingbo Ma <mayingbo5@gmail.com>", "Chris Rackauckas <accounts@chrisrackauckas.com> and contributors"]
-version = "8.71.2"
+version = "8.72.0"
 
 [deps]
 AbstractTrees = "1520ce14-60c1-5f80-bbc7-55ef81b5835c"

docs/src/tutorials/acausal_components.md

@@ -318,7 +318,7 @@ This is done as follows:
 u0 = [rc_model.capacitor.v => 0.0
     rc_model.capacitor.p.i => 0.0]
 
-prob = ODEProblem(sys, u0, (0, 10.0))
+prob = ODEProblem(rc_model, u0, (0, 10.0))
 sol = solve(prob, Rodas4())
 plot(sol)
 ```
@@ -331,7 +331,7 @@ letter `A`):
 u0 = [
     rc_model.capacitor.v => 0.0,
 ]
-prob = ODAEProblem(sys, u0, (0, 10.0))
+prob = ODAEProblem(rc_model, u0, (0, 10.0))
 sol = solve(prob, Rodas4())
 plot(sol)
 ```
@@ -344,7 +344,7 @@ like `structural_simplify` simply change state variables into observables which
 defined by `observed` equations.
 
 ```@example acausal
-observed(sys)
+observed(rc_model)
 ```
 
 These are explicit algebraic equations which can then be used to reconstruct