fix: Use correct type for actions parameter in ApplicationIntegrationToolset

Merge #2102

Addresses #2101

I've ran `pytest ./tests/unittests`, and all tests passed

COPYBARA_INTEGRATE_REVIEW=#2102 from manifoldtimblin:fix-type-hint 6d4ab72
PiperOrigin-RevId: 786046567

Author: manifoldtimblin

src/google/adk/tools/application_integration_tool/application_integration_toolset.py

@@ -87,7 +87,7 @@ def __init__(
       triggers: Optional[List[str]] = None,
       connection: Optional[str] = None,
       entity_operations: Optional[str] = None,
-      actions: Optional[str] = None,
+      actions: Optional[list[str]] = None,
       # Optional parameter for the toolset. This is prepended to the generated
       # tool/python function name.
       tool_name_prefix: Optional[str] = "",