Fix rbs:annotate task

rbs 3.10 cannot support rdoc < v6.16.
And rdoc v7 has been released.

Author: ksss

Gemfile

@@ -5,5 +5,5 @@ gem "test-unit"
 
 group :sig do
   gem "rbs"
-  gem "rdoc", "<= 6.11"
+  gem "rdoc"
 end

Rakefile

@@ -17,8 +17,8 @@ namespace :rbs do
     require "pathname"
 
     Dir.mktmpdir do |tmpdir|
-      system("rdoc --ri --output #{tmpdir}/doc --root=. lib")
-      system("rbs annotate --no-system --no-gems --no-site --no-home -d #{tmpdir}/doc sig")
+      sh("rdoc --ri --output #{tmpdir}/doc --root=. lib")
+      sh("rbs annotate --no-system --no-gems --no-site --no-home -d #{tmpdir}/doc sig")
     end
   end