FAQ: Added guide on suppressing #11682

This commit adds an instruction on how to suppress the error when deleting an Emacs package comes with system package manager.

Fixes #11682

doc/FAQ.org

@@ -47,6 +47,8 @@
   - [[#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]]
   - [[#why-do-the-fonts-look-crappy-on-windows][Why do the fonts look crappy on Windows?]]
   - [[#why-is-there-no-spacemacs-logo-in-the-startup-buffer][Why is there no Spacemacs logo in the startup buffer?]]
@@ -606,6 +608,19 @@ To fix this, add the following snippet to your ~user-config~:
   (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,
+or when you are trying to a package manually:
+
+#+BEGIN_EXAMPLE
+Package ‘PACKAGE-NAME’ is a system package, not deleting
+#+END_EXAMPLE
+
+it means this package comes with your distribution's package manager and is not installed by
+Spacemacs. You can suppress this by adding the package to =dotspacemacs-additional-packages=
+in your =.spacemacs= file.
+
 * Windows
 ** Why do the fonts look crappy on Windows?
 You can install [[https://code.google.com/archive/p/gdipp/][GDIPP]] (simplest) or [[https://code.google.com/p/mactype/][MacType]] (more complete) on Windows to get