remove custom roslyn plugin

lua/custom/plugins/roslyn.lua

@@ -1,8 +0,0 @@
-return {
-  'seblyng/roslyn.nvim',
-  ---@module 'roslyn.config'
-  ---@type RoslynNvimConfig
-  opts = {
-    -- your configuration comes here; leave empty for default settings
-  },
-}