Change subscript to a constant in visualizations file

[oameye]

Should resolve precompilation error on 1.12:

Failed to precompile DynamicalSystemsVisualizations [bf41aec9-21e8-5d35-8521-19f2dd369247] to "/home/oameye/.julia/compiled/v1.12/DynamicalSystemsVisualizations/jl_2VJbhP".
ERROR: LoadError: invalid assignment to constant DynamicalSystemsVisualizations.subscript. This redefinition may be permitted using the `const` keyword.
Stacktrace:
 [1] top-level scope
   @ ~/.julia/packages/DynamicalSystems/sv3mw/ext/DynamicalSystemsVisualizations.jl:14
 [2] include(mod::Module, _path::String)
   @ Base ./Base.jl:306
 [3] include_package_for_output(pkg::Base.PkgId, input::String, depot_path::Vector{String}, dl_load_path::Vector{String}, load_path::Vector{String}, concrete_deps::Vector{Pair{Base.PkgId, UInt128}}, source::Nothing)
   @ Base ./loading.jl:3021
 [4] top-level scope
   @ stdin:5
 [5] eval(m::Module, e::Any)
   @ Core ./boot.jl:489
 [6] include_string(mapexpr::typeof(identity), mod::Module, code::String, filename::String)
   @ Base ./loading.jl:2867
 [7] include_string
   @ ./loading.jl:2877 [inlined]
 [8] exec_options(opts::Base.JLOptions)
   @ Base ./client.jl:315
 [9] _start()
   @ Base ./client.jl:550
in expression starting at /home/oameye/.julia/packages/DynamicalSystems/sv3mw/ext/DynamicalSystemsVisualizations.jl:1
in expression starting at stdin:

[Datseris]

Yeap, I have a PR ongoing that also fixes that in #260 so I;ll close this one in favour of hte other. sorry please be a bit ore patient for sing in 1.12 (or use your fork for now!)

[oameye]

Ha I see. No worries :)