Trim length of E2E SAST report fixture

What does this MR do?

Trims the length of the SAST report fixture used by Secure E2E tests to reduce the page count of security reports and therefore reduce the reliance on filtering to display vulnerabilities for verification.

As per policy, does not un-quarantine the tests as they require several passing runs in a quarantined state.

Related to #34342 (closed).

Screenshots

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

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