Fix array query parameter serialization: use repeat format instead of comma format

OpenAPI spec uses style: form, explode: true for array parameters which requires
repeat format (?provider=openai&provider=anthropic) not comma format
(?provider=openai,anthropic)

Author: Dragos Nedelcu

src/not_diamond/_client.py

@@ -120,7 +120,7 @@ def __init__(
     @property
     @override
     def qs(self) -> Querystring:
-        return Querystring(array_format="comma")
+        return Querystring(array_format="repeat")
 
     @property
     @override
@@ -298,7 +298,7 @@ def __init__(
     @property
     @override
     def qs(self) -> Querystring:
-        return Querystring(array_format="comma")
+        return Querystring(array_format="repeat")
 
     @property
     @override