use benchmark not btime in brusselator example

Author: asinghvi17

docs/src/showcase/brusselator.md

@@ -252,15 +252,17 @@ assess this performance difference:
 
 ```@example bruss
 using BenchmarkTools
-@btime sol = solve(prob, TRBDF2(), saveat = 0.1);
-@btime sol = solve(prob_sparse, TRBDF2(), saveat = 0.1);
+@benchmark sol = solve(prob, TRBDF2(), saveat = 0.1);
+```
+```@example bruss
+@benchmark sol = solve(prob_sparse, TRBDF2(), saveat = 0.1);
 ```
 
 But we can further improve this as well. Instead of just using the default linear solver,
 we can change this to a Newton-Krylov method by passing in the GMRES method:
 
 ```@example bruss
-@btime sol = solve(prob_sparse, TRBDF2(linsolve = KrylovJL_GMRES()), saveat = 0.1);
+@benchmark sol = solve(prob_sparse, TRBDF2(linsolve = KrylovJL_GMRES()), saveat = 0.1);
 ```
 
 But to further improve performance, we can use an iLU preconditioner. This looks like
@@ -277,7 +279,7 @@ function incompletelu(W, du, u, p, t, newW, Plprev, Prprev, solverdata)
     Pl, nothing
 end
 
-@btime solve(prob_sparse,
+@benchmark solve(prob_sparse,
     TRBDF2(linsolve = KrylovJL_GMRES(), precs = incompletelu, concrete_jac = true),
     save_everystep = false);
 ```