How to disable flycheck warning while editing emacs lisp scripts?

If you wish to disable a particular Flycheck just for this one file, you can also use a file-local variable definition.

You can do this interactively while in the file's buffer by typing

  M-x add-file-local-variable flycheck-disabled-checkers RET
  (emacs-lisp-checkdoc)

which will add a local variables section to the end of the file.

;; Local Variables:
;; flycheck-disabled-checkers: (emacs-lisp-checkdoc)
;; End:

This is like customizing flycheck-disabled-checkers but only for the file.

This can also be customized on the level of the directory. http://www.gnu.org/software/emacs/manual/html_mono/emacs.html#Directory-Variables

These are Checkdoc warnings. To disable these, add emacs-lisp-checkdoc to the option flycheck-disabled-checkers, either with the following code in your init file

(with-eval-after-load 'flycheck
  (setq-default flycheck-disabled-checkers '(emacs-lisp-checkdoc)))

or via the customize interface with M-x customize-variable RET flycheck-disabled-checkers.