Update CHANGELOG.md for 12.0.8

[ci skip]

changelogs/unreleased/security-project-import-bypass.yml

----
-title: Fix project import restricted visibility bypass via API
-merge_request:
-author:
-type: security

changelogs/unreleased/security-sarcila-fix-weak-session-management.yml

----
-title: Fix weak session management by clearing password reset tokens after login (username/email)
-  are updated
-merge_request:
-author:
-type: security

changelogs/unreleased/security-ssrf-kubernetes-dns.yml

----
-title: Fix SSRF via DNS rebinding in Kubernetes Integration
-merge_request:
-author:
-type: security