fix broken shell link

See Raku/doc-website#270

Author: Márton Polgár

doc/Type/Proc.rakudoc

@@ -221,7 +221,7 @@ present in older releases.
 
 Runs the C<Proc> object with the given command and environment which are
 passed through to the shell for parsing and execution. See
-L<C<shell>|/language/independent-routines#sub_shell> for an explanation of which shells
+L<C<shell>|/type/independent-routines#sub_shell> for an explanation of which shells
 are used by default in the most common operating systems.
 
 =head2 method command