Delete support for the Conkeror web browser

The last release of Conkeror was in 2017.  The project has been actively
recommending people not to use it since 2019 due to security concerns,
and it was removed from Debian in the same year.  Emacs's browse-url
support for Conkeror has been obsolete since in Emacs 28.1.

* lisp/net/browse-url.el (browse-url-conkeror-new-window-is-buffer):
(browse-url-conkeror-program, browse-url-conkeror-arguments): Delete
variables.
(browse-url-conkeror): Delete function.

etc/NEWS

@@ -306,6 +306,9 @@ a web browser to load them.  For example, it could be used like this:
 For better integration with the Qutebrowser, set
 'browse-url(-secondary)-browser-function' to 'browse-url-qutebrowser'.
 
+*** Support for the Conkeror web browser has been removed.
+It has been obsolete since Emacs 28.1.
+
 ** CL-Lib
 
 +++

lisp/net/browse-url.el

@@ -403,16 +403,6 @@ If non-nil, then open the URL in a new tab rather than a new window if
 NEW-WINDOW argument."
   :type 'boolean)
 
-(defcustom browse-url-conkeror-new-window-is-buffer nil
-  "Whether to open up new Conkeror windows in a buffer or a new window.
-If non-nil, then open the URL in a new buffer rather than a new window if
-`browse-url-conkeror' is asked to open it in a new window via the
-NEW-WINDOW argument."
-  :version "25.1"
-  :type 'boolean)
-
-(make-obsolete-variable 'browse-url-conkeror-new-window-is-buffer nil "28.1")
-
 (defcustom browse-url-epiphany-new-window-is-tab nil
   "Whether to open up new Epiphany windows in a tab or a new window.
 If non-nil, then open the URL in a new tab rather than a new window if
@@ -434,20 +424,6 @@ Passing an interactive argument to \\[browse-url], or specific browser
 commands reverses the effect of this variable."
   :type 'boolean)
 
-(defcustom browse-url-conkeror-program "conkeror"
-  "The name by which to invoke Conkeror."
-  :type 'string
-  :version "25.1")
-
-(make-obsolete-variable 'browse-url-conkeror-program nil "28.1")
-
-(defcustom browse-url-conkeror-arguments nil
-  "A list of strings to pass to Conkeror as arguments."
-  :version "25.1"
-  :type '(repeat (string :tag "Argument")))
-
-(make-obsolete-variable 'browse-url-conkeror-arguments nil "28.1")
-
 (defcustom browse-url-filename-alist
   `(("^/\\(ftp@\\|anonymous@\\)?\\([^:/]+\\):/*" . "ftp://\\2/")
     ;; The above loses the username to avoid the browser prompting for
@@ -1504,46 +1480,6 @@ used instead of `browse-url-new-window-flag'."
 
 (function-put 'browse-url-gnome-moz 'browse-url-browser-kind 'external)
 
-;; --- Conkeror ---
-;;;###autoload
-(defun browse-url-conkeror (url &optional new-window)
-  "Ask the Conkeror WWW browser to load URL.
-Default to the URL around or before point.  Also pass the strings
-in the variable `browse-url-conkeror-arguments' to Conkeror.
-
-When called interactively, if variable
-`browse-url-new-window-flag' is non-nil, load the document in a
-new Conkeror window, otherwise use a random existing one.  A
-non-nil interactive prefix argument reverses the effect of
-`browse-url-new-window-flag'.
-
-If variable `browse-url-conkeror-new-window-is-buffer' is
-non-nil, then whenever a document would otherwise be loaded in a
-new window, load it in a new buffer in an existing window instead.
-
-When called non-interactively, use optional second argument
-NEW-WINDOW instead of `browse-url-new-window-flag'."
-  (declare (obsolete nil "28.1"))
-  (interactive (browse-url-interactive-arg "URL: "))
-  (setq url (browse-url-encode-url url))
-  (let* ((process-environment (browse-url-process-environment)))
-    (apply #'start-process (format "conkeror %s" url)
-	   nil
-	   browse-url-conkeror-program
-	   (append
-	    browse-url-conkeror-arguments
-	    (list
-	     "-e"
-	     (format "load_url_in_new_%s('%s')"
-		     (if (browse-url-maybe-new-window new-window)
-			 (if browse-url-conkeror-new-window-is-buffer
-			     "buffer"
-			   "window")
-		       "buffer")
-		     url))))))
-
-(function-put 'browse-url-conkeror 'browse-url-browser-kind 'external)
-
 ;; --- W3 ---
 
 ;; External.