docs: add note about client tokens changing with v 4.10

website/docs/reference/api-tokens-and-client-keys.mdx

@@ -42,7 +42,7 @@ Support for scoped admin tokens with more fine-grained permissions is currently
 - Register applications with the Unleash server
 - Send usage metrics
 
-When creating a client token, you can choose which projects it should be able to read data from. You can give it access to a specific list of projects or to all projects (including projects that don't exist yet).
+When creating a client token, you can choose which projects it should be able to read data from. You can give it access to a specific list of projects or to all projects (including projects that don't exist yet). Prior to Unleash 4.10, a token could be valid only for a *single project* or *all projects*.
 
 Each client token is only **valid for a single environment**.