add environment limitations (#5058)

Author: imatwawana

src/docs/product/security-policy-reporting.mdx

@@ -62,7 +62,7 @@ In addition to the `sentry_key` parameter, you may also pass the following withi
 
 `sentry_environment`
 
-: The environment name (e.g. production).
+: The environment name (e.g. production). The environment name can't contain newlines, spaces, or forward slashes, can't be the string "None", or exceed 64 characters. Also, environments are case sensitive. 
 
 `sentry_release`