fix: use delete=False for NamedTemporaryFile in tests on Windows

[athifmuhammad1001-svg]

Fixes #676 tests failing on Windows due to NamedTemporaryFile locking.

On Windows, NamedTemporaryFile locks the file while open, causing
PermissionError when the code tries to read it. Adding delete=False
resolves this.

Fixes: 8 failing tests on Windows

• test_client_generate_images
• test_client_create_blob
• test_client_create_blob_exists
• test_async_client_generate_images
• test_async_client_create_blob
• test_async_client_create_blob_exists
• test_image_serialization_path
• test_image_serialization_string_path

[aglpy]

This fix solves the Windows issue, but since delete=False is used, the temp image files won’t be deleted automatically and may be left on disk.

Maybe it would be better to wrap this in a try/finally block and remove the file manually after it has been used.

Don’t you think?