Fixed the flaky tests

What does this MR do?

Fixes the flaky tests mentioned in #299405 (closed). All of those are related to what seems like the absence of the content in the editor. This MR replaces those checks with proper editor's content checks.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Related to #299405 (closed), #299401 (closed), #299051 (closed), #297347 (closed), #297400 (closed)