Clarify casing change in documentation (#5834)

doc/governance/gov_api_schemas/upgrading_from_classic.rst

@@ -84,6 +84,8 @@ Ballots
 Member Activation
 -----------------
 
+.. note:: The payload casing has changed, ``state_digest`` has become ``stateDigest``.
+
 .. list-table::
    :align: left
 
@@ -248,4 +250,4 @@ Service State
    * - Replacement
      - :http:GET:`/gov/service/jwk`
    * - Notes
-     - | Single endpoint replaces multiple previous endpoints.
+     - | Single endpoint replaces multiple previous endpoints.