E2E: Remove sleep from invite_members_modal

What does this MR do and why?

Now that https://gitlab.com/gitlab-org/gitlab/-/issues/349379 has been resolved with #418905 (closed), this MR removes the extra sleep added as a workaround for this bug.

I have also verified #419163 (closed) will now pass on preprod without the workaround as well by removing the sleep and running the test locally several times against that environment.

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Checkout this branch locally
2. cd into qa
3. Run the following command to run invite_group_to_project_spec against preprod. See https://ops.gitlab.net/gitlab-org/quality/preprod/-/settings/ci_cd to get the values for the env variables.

GITLAB_USERNAME=gitlab-qa GITLAB_PASSWORD=<get from ops> GITLAB_QA_USERNAME_1=gitlab-qa-user1 GITLAB_QA_PASSWORD_1=<get from ops> GITLAB_QA_USER_AGENT=<get from ops> GITLAB_QA_ACCESS_TOKEN=<get from ops> WEBDRIVER_HEADLESS=false QA_GITLAB_URL=https://pre.gitlab.com bundle exec rspec qa/specs/features/browser_ui/9_data_stores/project/invite_group_to_project_spec.rb

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.