Remove {\rm ...} constructs.

Doc/lib/libposix.tex

@@ -459,7 +459,7 @@ Remove the file \var{path}.  This is the same function as \code{remove};
 the \code{unlink} name is its traditional \UNIX{} name.
 \end{funcdesc}
 
-\begin{funcdesc}{utime}{path, {\rm (}atime, mtime{\rm )}}
+\begin{funcdesc}{utime}{path, (atime, mtime)}
 Set the access and modified time of the file to the given values.
 (The second argument is a tuple of two items.)
 \end{funcdesc}