[istream.unformatted] add missing semi-colon to list item (#7117)

Author: jwakely

source/iostreams.tex

@@ -5408,7 +5408,7 @@
 \item
 \tcode{n != numeric_limits<streamsize>::max()}\iref{numeric.limits}
 and
-\tcode{n} characters have been extracted so far
+\tcode{n} characters have been extracted so far;
 \item
 end-of-file occurs on the input sequence
 (in which case the function calls