Update GDI-SOP_information-service-management.md

[silviabah]

Adding approvers information

Summary

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New content (non-breaking change which adds new content)
• Modified content (non-breaking change which modifies existing content)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Motivation and Context

References

Changes Introduced

Review

Additional Notes

Checklist:

General Compliance:

• My changes follow the code style of this project (GDI SOP Style Guide) and the file naming conventions of the file accessioning proposal.
• I have verified that all new updated content is accessible, including checking that all external references are readable (i.e., no broken links). These may include references to external resources that should be resolvable, and internal references among SOPs.
• I have properly added this PR's changes to the repository CHANGELOG.md.

Only applicable if the PR includes new, or changes to, GDI SOPs (i.e., documents at sops/):

• My SOP-related changes adhere to the Generic SOP Template, including format and required fields.
• I have consulted the Charter, ISM, and ORR documents to ensure compliance.
• I am complying with the established procedure for SOP creations and modifications, including respecting review phases and notifying needed contributors for reviews.