Phrase repair.

Doc/lib/libtime.tex

@@ -237,7 +237,7 @@ specification, and are replaced by the indicated characters in the
   \lineiii{\%X}{Locale's appropriate time representation.}{}
   \lineiii{\%y}{Year without century as a decimal number [00,99].}{}
   \lineiii{\%Y}{Year with century as a decimal number.}{}
-  \lineiii{\%Z}{Time zone name (or by no characters if no time zone exists).}{}
+  \lineiii{\%Z}{Time zone name (no characters if no time zone exists).}{}
   \lineiii{\%\%}{A literal \character{\%} character.}{}
 \end{tableiii}