Switch to PATs disabled env variable

What does this MR do and why?

After Update FedRamp PAT creation to be an Applicatio... (#384201 - closed) was updated, specs should follow the application logic and switch to using UI not when FIPS=1.

This helps to unblock FIPS QA pipelines from failures: omnibus-gitlab#7346 (comment 1201651127)

• Issue: gitlab-org/quality/quality-engineering/team-tasks#1570 (closed)
• Follow up on Enable Sanity tests to run on FIPS mode (!101663 - merged)

How to set up and validate locally

1. Run test as usual - ensure that it uses PATs

   WEBDRIVER_HEADLESS=false bundle exec bin/qa Test::Instance::All http://gdk.test:3000/ -- qa/specs/features/browser_ui/2_plan/issue/create_issue_spec.rb:26

2. Run test in PATS disabled mode - take a note that only UI methods are used in spec

   PERSONAL_ACCESS_TOKENS_DISABLED=true WEBDRIVER_HEADLESS=false bundle exec bin/qa Test::Instance::All http://gdk.test:3000/ -- qa/specs/features/browser_ui/2_plan/issue/create_issue_spec.rb:26

MR acceptance checklist

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