Fix issuables list search filter on labels

What does this MR do?

Repro:

• rails c
• Feature.enable(:vue_issuables_list)
• Go to project issues
• Filter labels and milestones by using !=.

As a result of adding Vue Issuables List to projects, a lot of specs failed and the FF was turned off in the following specs. When trying to turn on specs for:

• spec/features/issues/filtered_search/filter_issues_spec.rb
• spec/features/projects/labels/issues_sorted_by_priority_spec.rb

I noticed that the api call for vue issuables list was using deprecated params when calling the api, breaking some existing functionality. This MR resolves a few of the specs we needed to and fixes the params issue.

Screenshots

Before

After

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

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team