Updates migration docs

docs/migration/migrate_8_0.asciidoc

@@ -48,6 +48,12 @@ for example, `logstash-*`.
 
 *Impact:* To allow Kibana to function for these legacy browsers, set `csp.strict: false`. Since this is about enforcing a security protocol, we *strongly discourage* disabling `csp.strict` unless it is critical that you support Internet Explorer 11.
 
+[float]
+==== Configuring content security policy rules is no longer supported
+*Details:* Configuring `csp.rules` is removed in favor of per-directive specific configuration. Configuring the default `csp.script_src`, `csp.workers_src` and `csp.style_src` values is not required.
+
+*Impact:* Configure per-directive sources instead. See https://github.com/elastic/kibana/pull/102059 for more details.
+
 [float]
 ==== Default logging timezone is now the system's timezone
 *Details:* In prior releases the timezone used in logs defaulted to UTC. We now use the host machine's timezone by default.