[O] small typo in docstring for org-icalendar.el

[Stephen Eglen]

Typo and suggested change in docstring.

*** /var/folders/ix/ixcktwmzGyyc6z4C5D4ypU+++TI/-Tmp-/ediff3069aCw      
2012-04-03 22:31:26.000000000 +0100
--- /Users/stephen/langs/emacs/elisp-ds/org-mode/lisp/org-icalendar.el  
2012-04-03 22:08:47.000000000 +0100
***************
*** 194,200 ****
  
  (defcustom org-icalendar-timezone (getenv "TZ")
    "The time zone string for iCalendar export.
! When nil of the empty string, use the abbreviation retrieved from Emacs."
    :group 'org-export-icalendar
    :type '(choice
          (const :tag "Unspecified" nil)
--- 194,200 ----
  
  (defcustom org-icalendar-timezone (getenv "TZ")
    "The time zone string for iCalendar export.
! When nil or the empty string, use output from \(current-time-zone\)."
    :group 'org-export-icalendar
    :type '(choice
          (const :tag "Unspecified" nil)