[filebuf.members,fs.path.req] Fix indefinite article (#7530)

source/iostreams.tex

@@ -11226,7 +11226,7 @@
 \begin{itemdescr}
 \pnum
 \expects
-\tcode{s} points to a NTCTS\iref{defns.ntcts}.
+\tcode{s} points to an NTCTS\iref{defns.ntcts}.
 
 \pnum
 \effects
@@ -14079,14 +14079,14 @@
 \item \tcode{basic_string_view<EcharT, traits>}. A function
   argument \tcode{const Source\&} \tcode{source} shall have an
   effective range \range{source.begin()}{source.end()}.
-\item A type meeting the \oldconcept{InputIterator} requirements that iterates over a NTCTS\@.
+\item A type meeting the \oldconcept{InputIterator} requirements that iterates over an NTCTS\@.
   The value type shall be an encoded character type. A function argument
   \tcode{const Source\&} \tcode{source} shall have an effective range
   \range{source}{end} where \tcode{end} is the first
   iterator value with an element value equal to
   \tcode{iterator_traits<Source>::value_type()}.
 \item A character array that after array-to-pointer decay results in a
-  pointer to the start of a NTCTS\@. The value type shall be an encoded character type. A
+  pointer to the start of an NTCTS\@. The value type shall be an encoded character type. A
   function argument \tcode{const Source\&} \tcode{source} shall
   have an effective range \range{source}{end} where
   \tcode{end} is the first iterator value with an element value equal to