Page size and token no longer optional in pagination Params (#45)

Removed the initialisation to None for the parameters `page_size` and
`page_token` in pagination `Params` as they are no longer optional due
to the change in
frequenz-floss/frequenz-api-common#232

This PR fixes the CI failures in #44

Author: cyiallou

RELEASE_NOTES.md

@@ -2,11 +2,11 @@
 
 ## Summary
 
-<!-- Here goes a general summary of what this release is about -->
+Update of the Pagination `Params` data class.
 
 ## Upgrading
 
-<!-- Here goes notes on how to upgrade from previous versions, including deprecations and what they should be replaced with -->
+* Pagination `Params` has been changed such that the `page_size` and `page_token` fields are now no longer optional.
 
 ## New Features
 

src/frequenz/client/common/pagination/__init__.py

@@ -19,10 +19,10 @@
 class Params:
     """Parameters for paginating list requests."""
 
-    page_size: int | None = None
+    page_size: int
     """The maximum number of results to be returned per request."""
 
-    page_token: str | None = None
+    page_token: str
     """The token identifying a specific page of the list results."""
 
     @classmethod