ox-latex: Remove spurious newline in labels

* lisp/ox-latex.el (org-latex--caption/label-string): Remove spurious
  newline in labels.

Reported-by: Thomas S. Dye <tsd@tsdye.com>
<http://permalink.gmane.org/gmane.emacs.orgmode/105356>

lisp/ox-latex.el

@@ -1222,7 +1222,7 @@ For non-floats, see `org-latex--wrap-label'."
      ((org-string-nw-p caption-from-attr-latex)
       (concat caption-from-attr-latex "\n"))
      ((and (not main) (equal label "")) "")
-     ((not main) (concat label "\n"))
+     ((not main) label)
      ;; Option caption format with short name.
      (t
       (format (if nonfloat "\\captionof{%s}%s{%s%s}\n"