Improve service return type test

The following discussion from !4090 (merged) should be addressed:

• @kkloss started a discussion: (+4 comments)

  WDYT about using a context for each in the GDK::Services.all still?

      GDK::Services.all.each do |service|
        context service.class.name do
          it 'has expected return types', :aggregate_failures do

  If I change the Vite command back to an array, we get this error

    1) GDK::Services.all every service has expected return types
       Failure/Error: expect(service.command).to be_kind_of(String)
         expected ["support/exec-cd", "gitlab", "bundle", "exec", "vite", "dev"] to be a kind of String
       # ./spec/lib/gdk/services_spec.rb:39:in `block (5 levels) in <top (required)>'
       # ./spec/lib/gdk/services_spec.rb:37:in `each'
       # ./spec/lib/gdk/services_spec.rb:37:in `block (4 levels) in <top (required)>'

  However, that doesn’t tell me in which service the error occurred. Here we can tell from the command but what > if it is nil (-> expected nil to be a kind of String)?

  With the suggestion, the error would be more precise:

    1) GDK::Services.all GDK::Services::Vite has expected return types
       Failure/Error: expect(service.command).to be_kind_of(String)
         expected ["support/exec-cd", "gitlab", "bundle", "exec", "vite", "dev"] to be a kind of String
       # ./spec/lib/gdk/services_spec.rb:43:in `block (5 levels) in <top (required)>'

  Note that we’d have to stub the gdk.yml:

    before do
      stub_gdk_yaml({})
    end