Fix ruff issue and remove windows workflow

Author: Shashikant86

.github/workflows/ci.yml

@@ -49,7 +49,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-latest, macos-latest, windows-latest]
+        os: [ubuntu-latest, macos-latest]
         python-version: ["3.10", "3.11", "3.12", "3.13"]
 
     steps:

tests/test_export_import.py

@@ -8,7 +8,7 @@
 
 import pytest
 
-from dspy_code.core.exceptions import ExportError, ImportError, InvalidFormatError
+from dspy_code.core.exceptions import ExportError, ImportError
 from dspy_code.export import ExportImportHandler, PackageBuilder, PackageMetadata