correct brace

tagpdf-struct.dtx

@@ -1952,7 +1952,7 @@
 % The first argument is the number of the structure, 
 % the second a keyword referring to a function,
 % the third the value. Currently the existing keywords are all related
-% to the \texttt{Ref} key (an array}. 
+% to the \texttt{Ref} key (an array). 
 % The keyword \texttt{ref} takes as value an explicit object reference to 
 % a structure. The keyword \texttt{ref_label} expects as value a label name (from
 % a label set in a \cs{tagstructbegin} command). The keyword \texttt{ref_dest}