Ensure that spec/features/issues/user_uses_slash_commands_spec tests run locally

What does this MR do?

Ensure that the gitlab user is properly logged out before signing in in some tests in spec/features/issues/user_uses_slash_commands_spec.rb

Similar fix to https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/18687

Are there points in the code the reviewer needs to double check?

• No

Why was this MR needed?

When I ran bin/spring rspec ./spec/features/issues/user_uses_slash_commands_spec.rb on bba847fe locally, I got the following errors:

...............................F...F
Failures:


Issues > User uses quick actions issue-only commands move the issue to another project when the project is valid moves the issue
Failure/Error:
page.within(".js-main-target-form") do
fill_in("note[note]", with: text)
find(".js-comment-submit-button").click
end
Capybara::ElementNotFound:
Unable to find visible css ".js-main-target-form"

./spec/support/helpers/features/notes_helpers.rb:17:in `block in add_note'

./spec/support/helpers/features/notes_helpers.rb:16:in `add_note'

./spec/features/issues/user_uses_slash_commands_spec.rb:169:in `block (5 levels) in <top (required)>'

-e:1:in `'


Issues > User uses quick actions issue-only commands move the issue to another project when the user issues multiple commands moves the issue and applies the commands to both issues
Failure/Error:
page.within(".js-main-target-form") do
fill_in("note[note]", with: text)
find(".js-comment-submit-button").click
end
Capybara::ElementNotFound:
Unable to find visible css ".js-main-target-form"

./spec/support/helpers/features/notes_helpers.rb:17:in `block in add_note'

./spec/support/helpers/features/notes_helpers.rb:16:in `add_note'

./spec/features/issues/user_uses_slash_commands_spec.rb:247:in `block (5 levels) in <top (required)>'

-e:1:in `'


Finished in 4 minutes 12.7 seconds (files took 1.89 seconds to load)
36 examples, 2 failures

Does this MR meet the acceptance criteria?

• Review
  • Has been reviewed by Backend
• Conform by the style guides

What are the relevant issue numbers?

Closes #45970 (closed)