[RUN-AS-IF-FOSS]Fix confirmation modal showing on project

What does this MR do?

The confirmation modal is supposed to be shown on the group and instance level integration forms when "Save changes" is clicked. A bug in the frontend code caused this to show on project level integrations when the option "Use default settings" was selected. This MR fixes this.

Steps to replicate

• Setup a group (Group > Settings > Integrations - /groups/:namespace/-/settings/integrations/slack/edit) or instance (Admin > Settings > Integrations - /admin/application_settings/integrations/slack/edit) level integration.
• Go to Project > Settings > Integrations (/:namespace/:project/-/services/slack/edit).
• Select Use default settings in the dropdown.
• Click on Save changes. Observe that the form is saving directly without showing a modal.

Screenshots (strongly suggested)

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