selectrum: remove side effect in irc jump function
selectrum: remove side effect in irc jump function

`+irc/selectrum-jump-to-channel` previously modified
`+irc--consult-circe-source` in the definition, since `plist-put`, and I
quote from the manual:
"[] may modify plist destructively, or [] may construct a new list
structure without altering the old."

hlissner/.emacs.d,hlissner/doom-emacs,hlissner/doom-emacs,hlissner/doom-emacs,hlissner/.emacs.d,hlissner/.emacs.d,hlissner/.emacs.d,hlissner/doom-emacs,hlissner/doom-emacs,hlissner/.emacs.d,hlissner/.emacs.d,hlissner/.emacs.d,hlissner/doom-emacs,hlissner/doom-emacs,hlissner/.emacs.d