fix(editor): switch from vertico to selectrum due lsp-mode issue

First time lsp-mode is started for a project, it will pop up a prompt to
ask how you want lsp-mode to determine the project root. When using
vertico, this selection is not visible, while with selectrum it works
fine.

core/siren-core-modules.el

@@ -44,7 +44,7 @@
 (require 'siren-which-key)
 
 ;; Completion Systems and Interfaces
-(require 'siren-vertico)
+(require 'siren-selectrum)
 (require 'siren-orderless)
 
 ;; Linting