Update brusselator.md

Alex,

There is a typos
At line 137 & line 146, the position of the variable time, here described using the indices (k),  should be at the 3rd position as in solu = sol[u(x, y, t)] and in solv = sol[v(x, y, t)]
I  had also to remove the plots directory in 139 & line 148 and left only the just created gif file. 
This way the example runs perfectly.

Naceur

Author: naceurCRAAG

docs/src/tutorials/brusselator.md

@@ -134,17 +134,17 @@ For `u`:
 ```julia
 using Plots
 anim = @animate for k in 1:length(discrete_t)
-    heatmap(solu[k, 2:end, 2:end], title="$(discrete_t[k])") # 2:end since end = 1, periodic condition
+    heatmap(solu[2:end, 2:end, k], title="$(discrete_t[k])") # 2:end since end = 1, periodic condition
 end
-gif(anim, "plots/Brusselator2Dsol_u.gif", fps = 8)
+gif(anim, "Brusselator2Dsol_u.gif", fps = 8)
 ```       
 ![Brusselator2Dsol_u](https://user-images.githubusercontent.com/9698054/159934498-e5c21b13-c63b-4cd2-9149-49e521765141.gif)
 
 For `v`:
 ```julia
 anim = @animate for k in 1:length(discrete_t)
-    heatmap(solv[k, 2:end, 2:end], title="$(discrete_t[k])")
+    heatmap(solv[k, 2:end, 2:end, k], title="$(discrete_t[k])")
 end
-gif(anim, "plots/Brusselator2Dsol_v.gif", fps = 8)
+gif(anim, "Brusselator2Dsol_v.gif", fps = 8)
 ```       
 ![Brusselator2Dsol_v](https://i.imgur.com/3kQNMI3.gif)