Remove obsolete documentation in FAQ.org. (#15632)

doc/FAQ.org

@@ -18,7 +18,6 @@
   - [[#should-i-place-my-settings-in-user-init-or-user-config][Should I place my settings in =user-init= or =user-config=?]]
   - [[#why-do-some-of-my-org-related-settings-cause-problems][Why do some of my =org=-related settings cause problems?]]
   - [[#why-is-spacemacs-hanging-on-startup][Why is Spacemacs hanging on startup?]]
-  - [[#why-does-helm-m-x-spc-spc-not-accept-the-prefix-argument][Why does =helm-M-x= (~SPC SPC~) not accept the prefix argument?]]
   - [[#why-does-my-color-theme-not-render-correctly-in-terminal-mode][Why does my color theme not render correctly in terminal mode?]]
   - [[#typing-quickly-fd-takes-me-out-of-insert-state-what-is-going-on][Typing quickly =fd= takes me out of =insert state=. What is going on?]]
   - [[#why-do-i-get-files-starting-with-][Why do I get files starting with .#?]]
@@ -46,7 +45,6 @@
   - [[#make-copypaste-working-with-the-mouse-in-x11-terminals][Make copy/paste working with the mouse in X11 terminals?]]
   - [[#use-helm-ag-to-search-only-in-files-of-a-certain-type][Use =helm-ag= to search only in files of a certain type?]]
   - [[#modify-spacemacs-documentation-look-space-doc-mode][Modify spacemacs documentation look (space-doc-mode)]]
-  - [[#remap-paste-key-to-be-able-to-paste-copied-text-multiple-times][Remap paste key to be able to paste copied text multiple times]]
 - [[#linux][Linux]]
   - [[#error-on-deleting-a-system-package][Error on deleting a system package]]
 - [[#windows][Windows]]
@@ -199,17 +197,6 @@ not working, you can try to put these settings directly in =~/.ssh/config=:
   ControlPersist = no
 #+END_SRC
 
-** Why does =helm-M-x= (~SPC SPC~) not accept the prefix argument?
-If you try to run =helm-M-x= with the prefix argument (i.e. ~SPC u SPC SPC~) it
-will fail with this message:
-
-#+BEGIN_VERSE
-  Error: Specifying a prefix arg before calling helm-M-x
-#+END_VERSE
-
-Instead, call =helm-M-x= first, select the command you want to run, and press
-~C-u~ before pressing ~RETURN~. For instance: ~SPC SPC org-reload C-u RET~
-
 ** Why does my color theme not render correctly in terminal mode?
 In the terminal version of Emacs, color themes will not render correctly as
 colors are rendered by the terminal and not by emacs. You will probably have to
@@ -393,7 +380,7 @@ binding in the mode's map, e.g. for =magit-status-mode=,
 
 ** Include underscores and dashes in word motions?
 If you want =*= and =#= searches to include underscores and dashes as a
-part of a word, add ~(setq-default evil-symbol-word-search t)~ to your 
+part of a word, add ~(setq-default evil-symbol-word-search t)~ to your
 =dotspacemacs/user-config=.
 
 For other motions, you can modify the syntax table of the mode in question
@@ -593,21 +580,6 @@ By default only =center-buffer-mode= is disabled.
 Both =space-doc-mode= and =center-buffer-mode= can be customized
 with "Easy Customization Interface".
 
-** Remap paste key to be able to paste copied text multiple times
-In vim and evil, pasting over a text would cause it to be copied, hence making it impossible to paste
-the same text multiple times.
-
-To fix this, add the following snippet to your ~user-config~:
-
-#+BEGIN_SRC emacs-lisp
-  (defun evil-paste-after-from-0 ()
-    (interactive)
-    (let ((evil-this-register ?0))
-      (call-interactively 'evil-paste-after)))
-
-  (define-key evil-visual-state-map "p" 'evil-paste-after-from-0)
-#+END_SRC
-
 * Linux
 ** Error on deleting a system package
 If you see the an error message when either Spacemacs is trying to delete an orphaned package,