Fix mypy import errors: use relative imports in test_imports.py

- Changed from absolute import 'from activities import' to relative import 'from .activities import'
- This resolves mypy errors: Module 'activities' has no attribute 'complex_failing_activity' and 'failing_activity'
- Follows the same import pattern used in workflows.py and other sample files
- All local lint checks now pass: black, isort, and mypy

Co-Authored-By: deepika awasthi <deepika.awasthi@temporal.io>

Author: devin-ai-integration[bot]

multiline_logging/test_imports.py

@@ -8,7 +8,7 @@
 
     print("✅ Interceptor imports successfully")
 
-    from activities import complex_failing_activity, failing_activity
+    from .activities import complex_failing_activity, failing_activity
 
     print("✅ Activities import successfully")