fix TestGetFSTypeOfInvalidPath

Signed-off-by: Kirtana Ashok <kiashok@microsoft.com>
diff --git a/pkg/fs/fs_windows_test.go b/pkg/fs/fs_windows_test.go
index 512b235..f8c771d 100644
--- a/pkg/fs/fs_windows_test.go
+++ b/pkg/fs/fs_windows_test.go
@@ -17,7 +17,9 @@
 }
 
 func TestGetFSTypeOfInvalidPath(t *testing.T) {
-	_, err := GetFileSystemType("7:\\")
+	// [filepath.VolumeName] doesn't mandate that the drive letters matches [a-zA-Z].
+	// Instead, use non-character drive.
+	_, err := GetFileSystemType(`No:\`)
 	if err != ErrInvalidPath {
 		t.Fatalf("Expected `ErrInvalidPath`, got %v", err)
 	}