docs: fix "it's" to "its" (possessive) in README files

[syukawa-gh]

Issue

N/A (self-discovered grammar errors)

Reason for this change

Several README files incorrectly use "it's" (contraction of "it is") where "its" (possessive form) is intended.

Description of changes

• aws-chatbot/README.md: "it's expiration" → "its expiration"
• aws-rds/README.md: "it's utilization" → "its utilization"
• custom-resources/README.md: "it's value" → "its value", "it's last state" → "its last state"

Description of how you validated changes

Documentation-only changes. No functional impact.

Checklist

• My code adheres to the CONTRIBUTING GUIDE and DESIGN GUIDELINES

[mergify]

Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).

[mergify]

Merge Queue Status

• ✅ Entered queue — 2026-03-30 08:42 UTC · Rule: default-squash
• ✅ Checks passed · in-place
• ✅ Merged — 2026-03-30 11:54 UTC · at 0d803f991c8c02a0bdcb1c97bf7f8aebc5fd332c

This pull request spent 3 hours 11 minutes 20 seconds in the queue, including 45 minutes 51 seconds running CI.

Required conditions to merge

• #approved-reviews-by >= 1 [🛡 GitHub branch protection]
  • docs: fix "it's" to "its" (possessive) in README files #37402
• #changes-requested-reviews-by = 0 [🛡 GitHub branch protection]
  • docs: fix "it's" to "its" (possessive) in README files #37402
• any of [🛡 GitHub branch protection]:
  • check-success = validate-pr
  • check-neutral = validate-pr
  • check-skipped = validate-pr
• any of [🛡 GitHub branch protection]:
  • check-success = build
  • check-neutral = build
  • check-skipped = build

[mergify]

Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).

[mergify]

Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).

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