ox-latex: Exclude newline from labels within captions

* lisp/ox-latex.el (org-latex--caption/label-string): Exclude newline
character from labels within captions.

Reported-by: Godefroy <godefroy.vannoye@gmail.com>
<http://lists.gnu.org/r/emacs-orgmode/2019-10/msg00088.html>

lisp/ox-latex.el

@@ -1338,7 +1338,7 @@ For non-floats, see `org-latex--wrap-label'."
 		      (t (symbol-name type*)))
 		  ""))
 	      (if short (format "[%s]" (org-export-data short info)) "")
-	      label
+	      (org-trim label)
 	      (org-export-data main info))))))
 
 (defun org-latex-guess-inputenc (header)