Remove the reference to minicomputeres.

Documentation/chap-intro.tex

@@ -80,7 +80,7 @@ It is an interesting observation that in most text books on
 operating systems, the concept of a process is presented as playing
 a central role in operating-system design, whereas it ought to be
 presented as an unfortunate necessity due to the limited address
-space of existing minicomputers in the 1970s.  It is also presented
+space of existing computers in the 1970s.  It is also presented
 as \emph{the} method for obtaining some kind of \emph{security},
 preventing one application from intentionally or accidentally
 modifying the data of some other application.  In reality, there are