Delete nyxt/submodules

[aadcg]

Description

Thanks to the changes to the *.nix files, adding the element below to {sly,slime}-lisp-implementations

(nyxt-nix-electron
 ("nix-shell"
  ,(expand-file-name "/path/to/shell-electron.nix")
  "--run" "sbcl --dynamic-space-size 3072"))

enables a flexible dev env as exemplified below. Note that it's possible to override libraries marked as git submodules. Concretely ~/common-lisp/cl-lib overrides /path/to/nyxt/checkout/_build/cl-lib, where cl-lib is a dependency featured in .gitmodules. The approach works for both Linux and macOS.

(dolist (system '(:nasdf :nyxt :cl-electron :alexandria)) (print (nth-value 2 (asdf:locate-system system))))
=>
#P"/home/aadcg/common-lisp/nyxt/libraries/nasdf/nasdf.asd" 
#P"/home/aadcg/common-lisp/nyxt/nyxt.asd" 
#P"/home/aadcg/common-lisp/cl-electron/cl-electron.asd" 
#P"/home/aadcg/common-lisp/nyxt/_build/alexandria/alexandria.asd" 

Fixes #3374

Checklist:

• Git branch state is mergable.
• Changelog is up to date (via a separate commit).
• New dependencies are accounted for.
• Documentation is up to date.
• Compilation and tests ((asdf:test-system :nyxt/<renderer>))
  • No new compilation warnings.
  • Tests are sufficient.