fix(build): fix python runtime BaseProvider signatures (#601)

Author: RomainMuller

packages/jsii-python-runtime/src/jsii/_kernel/providers/base.py

@@ -74,7 +74,7 @@ def sinvoke(self, request: StaticInvokeRequest) -> InvokeResponse:
         ...
 
     @abc.abstractmethod
-    def complete(self, request: CompleteRequest) -> Union[InvokeResponse, GetResponse]:
+    def complete(self, request: CompleteRequest) -> CompleteResponse:
         ...
 
     @abc.abstractmethod
@@ -97,10 +97,6 @@ def end(self, request: EndRequest) -> EndResponse:
     def callbacks(self, request: CallbacksRequest) -> CallbacksResponse:
         ...
 
-    @abc.abstractmethod
-    def complete(self, request: CompleteRequest) -> CompleteResponse:
-        ...
-
     @abc.abstractmethod
     def stats(self, request: Optional[StatsRequest] = None) -> StatsResponse:
         ...