Checkdoc fixes in `erc/*.el`

Checkdoc fixes in `erc/*.el`

* lisp/erc/erc-backend.el (erc-server-parameters):
* lisp/erc/erc-button.el (erc-button--display-error-with-buttons):
* lisp/erc/erc-dcc.el (erc-dcc-member):
* lisp/erc/erc-fill.el (erc-fill-wrap-refill-buffer):
* lisp/erc/erc-speedbar.el (erc-speedbar--last-ran):
* lisp/erc/erc-stamp.el (erc-stamp--current-time):
* lisp/erc/erc-track.el (erc-make-mode-line-buffer-name):
* lisp/erc/erc.el (erc-interactive-display, erc-modules, erc-cmd-CLEAR)
(erc-update-current-channel-member, erc--format-user-modes)
(erc-check-text-conversion): Checkdoc fixes.

(cherry picked from commit c85f67a66dfc9b3333a466a5fcd313425889ee6e)