Update license terms in manpage

Author: lucab

man/rustc.1

@@ -170,5 +170,5 @@ See \fBAUTHORS.txt\fR in the rust source distribution. Graydon Hoare
 <\fI[email protected]\fR> is the project leader.
 
 .SH "COPYRIGHT"
-This work is licensed under MIT-like terms.  See \fBLICENSE.txt\fR
-in the rust source distribution.
+This work is dual-licensed under Apache 2.0 and MIT terms.  See \fBCOPYRIGHT\fR
+file in the rust source distribution.