Remove unnecessary comments from login tests

The comments were TODOs but there were no explanation of what
needed to be done.

Also, I think the expectation describes very well how it checks
that the user is logged in.

Finally, as Robert C. Martin said once:
"After you check in a TODO comment it turns into a DON'T DO"

qa/qa/specs/features/browser_ui/1_manage/login/log_in_spec.rb

@@ -7,16 +7,12 @@ module QA
         Runtime::Browser.visit(:gitlab, Page::Main::Login)
         Page::Main::Login.act { sign_in_using_credentials }
 
-        # TODO, since `Signed in successfully` message was removed
-        # this is the only way to tell if user is signed in correctly.
-        #
         Page::Main::Menu.perform do |menu|
           expect(menu).to have_personal_area
         end
 
         Page::Main::Menu.perform do |menu|
           menu.sign_out
-          expect(menu).not_to have_personal_area
         end
 
         Page::Main::Login.perform do |form|

qa/qa/specs/features/browser_ui/1_manage/login/log_into_gitlab_via_ldap_spec.rb

@@ -7,9 +7,6 @@ module QA
         Runtime::Browser.visit(:gitlab, Page::Main::Login)
         Page::Main::Login.act { sign_in_using_credentials }
 
-        # TODO, since `Signed in successfully` message was removed
-        # this is the only way to tell if user is signed in correctly.
-        #
         Page::Main::Menu.perform do |menu|
           expect(menu).to have_personal_area
         end

qa/qa/specs/features/browser_ui/1_manage/login/register_spec.rb

@@ -7,9 +7,6 @@ module QA
 
       Resource::User.fabricate_via_browser_ui!
 
-      # TODO, since `Signed in successfully` message was removed
-      # this is the only way to tell if user is signed in correctly.
-      #
       Page::Main::Menu.perform do |menu|
         expect(menu).to have_personal_area
       end