fix: move JSOSolvers import before subsolver list call

The code was trying to access JSOSolvers.trunkls_allowed_subsolvers before importing the JSOSolvers package, causing an UndefVarError. This moves the 'using JSOSolvers' statement before the subsolver list display.

Author: arnavk23

tutorials/introduction-to-jsosolvers/index.jmd

@@ -44,6 +44,10 @@ The solvers `tron` and `trunk` both have a specialized implementation for input
 
 The following examples illustrate this specialization.
 
+```julia
+using JSOSolvers, ADNLPModels
+```
+
 To list the allowed least-squares subsolvers for these specializations:
 
 ```julia
@@ -52,7 +56,6 @@ JSOSolvers.tronls_allowed_subsolvers
 ```
 
 ```julia
-using JSOSolvers, ADNLPModels
 f(x) = (x[1] - 1)^2 + 4 * (x[2] - x[1]^2)^2
 nlp = ADNLPModel(f, [-1.2; 1.0])
 trunk(nlp, atol = 1e-6, rtol = 1e-6)