module: remove :tools gist

This module had been deprecated for some years, because it's central
package (gist.el) has been non-functional and unmaintained for years.
This will later be replaced with a more general module (powered by
webpaste.el or similar) for interacting with pastebin
services (including gist).

templates/init.example.el

@@ -94,7 +94,6 @@
        ;;editorconfig      ; let someone else argue about tabs vs spaces
        ;;ein               ; tame Jupyter notebooks with emacs
        (eval +overlay)     ; run code, run (also, repls)
-       ;;gist              ; interacting with github gists
        lookup              ; navigate your code and its documentation
        ;;lsp               ; M-x vscode
        magit             ; a git porcelain for Emacs