Remove two flaky tests from smoke suite

What does this MR do?

Removes two tests with known intermittent failures from smoke suite. This is one of the required steps to make review-qa-smoke job more reliable before we make it mandatory in gitlab-com/www-gitlab-com#11568 (closed).

The following end-to-end tests were identified as flaky as part of smoke failure analysis:

• qa/specs/features/browser_ui/6_release/pages/pages_pipeline_spec.rb - see #300906
• qa/specs/features/browser_ui/4_verify/pipeline/create_and_process_pipeline_spec.rb - see #300909 (closed)

Does this MR meet the acceptance criteria?

Conformity

• [-] I have included a changelog entry, or it's not needed. (Does this MR need a changelog?)
• [-] I have added/updated documentation, or it's not needed. (Is documentation required?)
• [-] I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• [-] I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.