Sync version_6_upgrade.html.markdown (#11128) (#7701)

[upstream:48507d229ca7d8d444df782c64efaa0665f95cee]

Signed-off-by: Modular Magician <[email protected]>

Author: modular-magician

.changelog/11128.txt

@@ -0,0 +1,3 @@
+```release-note:none
+
+```

website/docs/guides/version_6_upgrade.html.markdown

@@ -113,3 +113,9 @@ Description of the change and how users should adjust their configuration (if ne
 ### `settings.ip_configuration.require_ssl` is now removed
 
 Removed in favor of field `settings.ip_configuration.ssl_mode`.
+
+## Resource: `google_pubsub_topic`
+
+### `schema_settings` no longer has a default value
+
+An empty value means the setting should be cleared.