Update overview.md

Update retirement date of legacy developer portal

Author: dlepow

articles/api-management/breaking-changes/overview.md

@@ -20,7 +20,7 @@ The following table lists all the upcoming breaking changes and feature retireme
 | [Resource provider source IP address updates][bc1] | March 31, 2023 |
 | [Resource provider source IP address updates][rp2023] | September 30, 2023 |
 | [API version retirements][api2023] | September 30, 2023 |
-| [Deprecated (legacy) portal retirement][devportal2023] | October 2023 |
+| [Deprecated (legacy) portal retirement][devportal2023] | October 31, 2023 |
 | [Self-hosted gateway v0/v1 retirement][shgwv0v1] | October 1, 2023 |
 | [stv1 platform retirement][stv12024] | August 31, 2024 |
 | [ADAL-based Azure AD or Azure AD B2C identity provider retirement][msal2025] | September 30, 2025 |