vimPlugins.neuron-vim: ihsanturk/neuron.vim -> fiatjaf/neuron.vim

The current derivation for `vimPlugins.neuron-vim` points to
[ihsanturk/neuron.vim], which doesn't seem to be actively maintained.
This PR switches over to an actively maintained fork,
[fiatjaf/neuron.vim], which works with recent versions of [neuron].

[ihsanturk/neuron.vim]: https://github.com/ihsanturk/neuron.vim
[fiatjaf/neuron.vim]: https://github.com/fiatjaf/neuron.vim
[neuron]: https://github.com/srid/neuron

pkgs/misc/vim-plugins/vim-plugin-names

@@ -109,6 +109,7 @@ fatih/vim-go
 fcpg/vim-osc52
 FelikZ/ctrlp-py-matcher
 fenetikm/falcon
+fiatjaf/neuron.vim
 fisadev/vim-isort
 flazz/vim-colorschemes
 floobits/floobits-neovim
@@ -159,7 +160,6 @@ iamcco/coc-vimlsp
 ianks/vim-tsx
 idanarye/vim-merginal
 idris-hackers/idris-vim
-ihsanturk/neuron.vim
 Inazuma110/deoplete-greek
 inkarkat/vim-SyntaxRange
 int3/vim-extradite