Added migration guide (#4123)

Author: mikefrobbins

docs-conceptual/azps-16.0.0/azureps-support-lifecycle.md

@@ -105,6 +105,7 @@ For detailed information about breaking changes in major releases of the **Az**
 see the following articles.
 
 - [Upcoming breaking changes](upcoming-breaking-changes.md)
+- [Az 16.0.0 breaking changes](migrate-az-16.0.0.md)
 - [Az 15.0.0 breaking changes](migrate-az-15.0.0.md)
 - [Az 14.0.0 breaking changes](migrate-az-14.0.0.md)
 - [Az 13.0.0 breaking changes](migrate-az-13.0.0.md)

docs-conceptual/azps-16.0.0/index.yml

@@ -52,8 +52,8 @@ landingContent:
             url: whats-new-overview.md
           - text: Release notes
             url: release-notes-azureps.md
-          - text: Az 15.0.0 migration guide
-            url: migrate-az-15.0.0.md
+          - text: Az 16.0.0 migration guide
+            url: migrate-az-16.0.0.md
           - text: Upcoming breaking changes
             url: upcoming-breaking-changes.md
           - text: Impact of MFA in automation