Pin internal events validation component to v1.1.3 on 19-3-stable-ee

What does this MR do and why?

Bumps the internal_events_validation CI component pin from v1.1.2 to v1.1.3 on 19-3-stable-ee.

The v1.1.2 validator resolves config/metrics/schema/product_groups.json from master instead of from the branch under test. Product groups renamed or removed upstream since 19.3 branched (e.g. security_platform_management → security_controls) therefore fail validation here, even though the event definitions are valid against this branch's own product_groups.json. As a result, any MR touching config/events or ee/config/events on this branch cannot pass internal-events-definitions-validation-ee.

v1.1.3 reads the file from $CI_PROJECT_DIR (the upstream fix in gitlab-org/analytics-section/analytics-instrumentation/event-definitions-validator#2 (closed)), so definitions are validated against the branch's own vocabulary.

v1.1.3 is used rather than v1.2.1 (which master and 19-4-stable-ee use) so that 19.2 and 19.3 can share the same pin: v1.2.1 adds a product_categories requirement that still rejects valid 19.2 definitions. 19.3 passes on both versions.

This is not a backport of a default-branch MR. master already pins v1.2.1 and is unaffected; the bug exists only on the stable branches. This is a CI configuration change and does not ship in a release artifact.

Related to #629529 (closed). A separate MR targets 19-2-stable-ee.

Validation

Measured per the issue, with the validator's first-failure short-circuit removed:

Validator	19-3-stable-ee rejected files
1.1.2 (current)	66
1.1.3 (this MR)	0

internal-events-definitions-validation-ee should pass on this MR's pipeline.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• This MR is backporting a bug fix, documentation update, or spec fix, previously merged in the default branch.
  • N/A: no default-branch MR exists; master is unaffected (see above).
• The MR that fixed the bug on the default branch has been deployed to GitLab.com (not applicable for documentation or spec changes).
  • N/A: same reason.
• The MR title is descriptive (e.g. "Backport of 'title of default branch MR'"). This is important, since the title will be copied to the patch blog post.
• Required labels have been applied to this merge request
  • severity label and bug subtype labels (if applicable)
  • If this MR fixes a bug that affects customers, the customer label has been applied.
• This MR has been approved by a maintainer (only one approval is required).
• Ensure the e2e:test-on-omnibus-ee E2E Omnibus GitLab EE pipeline has succeeded. If it has failed (or shows warnings), investigate the failures. If you determine the failures are unrelated, you may proceed. If you need assistance investigating, request help in the #s_developer_experience Slack channel to confirm the failures are unrelated to the merge request.

Note to the merge request author and maintainer

If you have questions about the patch release process, please:

• Refer to the patch release runbook for engineers and maintainers for guidance.
• Ask questions on the #releases Slack channel (internal only).

Once the backport has been merged, the commit changes will be automatically deployed to a release environment that can be used for manual validation. See the after merging runbook for details.