Fix typos in docstrings.

Fix typos in docstrings.

* image-dired.el (image-dired-display-thumbs): Fix typo in docstring.
  (image-dired-read-comment): Doc fix.

* json.el (json-object-type, json-array-type, json-key-type, json-false)
  (json-null, json-read-number):
* minibuffer.el (completion-in-region-functions):
* calendar/cal-tex.el (cal-tex-daily-end, cal-tex-number-weeks)
  (cal-tex-cursor-week):
* emacs-lisp/trace.el (trace-function):
* eshell/em-basic.el (eshell/printnl):
* eshell/em-dirs.el (eshell-last-dir-ring, eshell-parse-drive-letter)
  (eshell-read-last-dir-ring, eshell-write-last-dir-ring):
* obsolete/levents.el (allocate-event, event-key, event-object)
  (event-point, event-process, event-timestamp, event-to-character)
  (event-window, event-x, event-x-pixel, event-y, event-y-pixel):
* textmodes/reftex-vars.el (reftex-index-macros-builtin)
  (reftex-section-levels, reftex-auto-recenter-toc, reftex-toc-mode-hook)
  (reftex-cite-punctuation, reftex-search-unrecursed-path-first)
  (reftex-highlight-selection): Fix typos in docstrings.