Update CVE-2025-43857.yml

Added link to HackerOne report for GHSA-j3g3-5qv5-52mj / CVE-2025-43857.

Author: postmodern

gems/net-imap/CVE-2025-43857.yml

@@ -120,3 +120,4 @@ related:
     - https://github.com/ruby/net-imap/pull/447
     - https://nvd.nist.gov/vuln/detail/CVE-2025-43857
     - https://github.com/advisories/GHSA-j3g3-5qv5-52mj
+    - https://hackerone.com/reports/3108869