ox-latex: Properly escape special characters in tags

* lisp/ox-latex.el (org-latex-format-headline-default-function):
(org-latex-format-inlinetask-default-function): Use
`org-latex--protect-text' instead of `org-latex-plain-text' to format
tags.

lisp/ox-latex.el

@@ -2009,8 +2009,7 @@ See `org-latex-format-headline-function' for details."
    text
    (and tags
 	(format "\\hfill{}\\textsc{%s}"
-		(mapconcat (lambda (tag) (org-latex-plain-text tag info))
-			   tags ":")))))
+		(mapconcat #'org-latex--protect-text tags ":")))))
 
 
 ;;;; Horizontal Rule
@@ -2092,7 +2091,7 @@ holding contextual information."
 	     todo todo-type priority title tags contents info)))
 
 (defun org-latex-format-inlinetask-default-function
-  (todo _todo-type priority title tags contents info)
+    (todo _todo-type priority title tags contents info)
   "Default format function for a inlinetasks.
 See `org-latex-format-inlinetask-function' for details."
   (let ((full-title
@@ -2101,9 +2100,7 @@ See `org-latex-format-inlinetask-function' for details."
 		 title
 		 (when tags
 		   (format "\\hfill{}\\textsc{:%s:}"
-			   (mapconcat
-			    (lambda (tag) (org-latex-plain-text tag info))
-			    tags ":"))))))
+			   (mapconcat #'org-latex--protect-text tags ":"))))))
     (concat "\\begin{center}\n"
 	    "\\fbox{\n"
 	    "\\begin{minipage}[c]{.6\\textwidth}\n"