[APIM] Update maximum size limit for policy fragments

Per Teams thread/code

Author: dlepow

articles/api-management/policy-fragments.md

@@ -30,7 +30,7 @@ Limitations:
 
 * A policy fragment can't include a policy section identifier (`<inbound>`, `<outbound>`, for example) or the `<base/>` element.
 * Currently, a policy fragment can't nest another policy fragment. 
-* The maximum size of a policy fragment is 32 KB.
+* The maximum size of a policy fragment is 512 KB.
 
 ## Prerequisites