tools/gist: open gists in non-popups

- Removes +gist/kill-cache (gist-list and gist-list-user with a
  universal argument already does this).
- Removes +gist/open-current. No longer necessary when gists aren't
  opened in popups.
- Makes keybinds more consistent with other "porcelains", like elfeed's
  or magit.

modules/tools/gist/autoload/gist.el

@@ -1,16 +0,0 @@
-;;; tools/gist/autoload/gist.el -*- lexical-binding: t; -*-
-
-;;;###autoload
-(defun +gist/open-current ()
-  (interactive)
-  (gist-fetch-current)
-  (when-let* ((win (get-buffer-window "*github:gists*")))
-    (doom/popup-close win)))
-
-;;;###autoload
-(defun +gist/kill-cache ()
-  "Clears the gist cache. Necessary when a faulty cache causes gist.el to be
-entirely unuseable."
-  (interactive)
-  (delete-directory (expand-file-name "gh" pcache-directory) t)
-  (message "gist.el cache cleared"))