ruby-fakegem.eclass: use dodoc to install documentation files

dohtml is deprecated in EAPI 6, but more importantly it does not
actually do what we want, which is to install all the documentation
files, including fonts, javascript, and css to make the documentation
pages look as intended.

eclass/ruby-fakegem.eclass

@@ -505,7 +505,7 @@ all_fakegem_install() {
 			[[ -d ${dir} ]] || continue
 
 			pushd ${dir} &>/dev/null || die
-			dohtml -r * || die "failed to install documentation"
+			dodoc -r * || die "failed to install documentation"
 			popd &>/dev/null || die
 		done
 	fi