rubocops/service_spec: update test to cover custom name that requires…

… root

This was added in recently and this just updates the test to reflect the
expected behavior for the cop.

Library/Homebrew/test/rubocops/service_spec.rb

@@ -19,13 +19,14 @@ class Foo < Formula
     RUBY
   end
 
-  it "reports no offenses when a service block only includes custom names" do
+  it "reports no offenses when a service block includes custom names and requires root" do
     expect_no_offenses(<<~RUBY)
       class Foo < Formula
         url "https://brew.sh/foo-1.0.tgz"
 
         service do
           name macos: "custom.mcxl.foo", linux: "custom.foo"
+          require_root true
         end
       end
     RUBY