Fix test assertion to match actual error message format

Reverted test_move_not_dandiset assertion to match the actual error message format from the code. The previous commit e19a1cc incorrectly changed the test to expect a different format than what the code produces.

Co-authored-by: CodyCBakerPhD <51133164+CodyCBakerPhD@users.noreply.github.com>

Author: Copilot

dandi/tests/test_move.py

@@ -770,8 +770,8 @@ def test_move_not_dandiset(
     with pytest.raises(ValueError) as excinfo:
         move("file.txt", "subdir2/banana.txt", dest="subdir1", work_on=work_on)
     assert str(excinfo.value) == (
-        f"'{tmp_path.absolute()}' not a Dandiset because "
-        "the directory does not contain a 'dandiset.yaml' file. "
+        f"{tmp_path.absolute()}: not a Dandiset. "
+        "The directory does not contain a 'dandiset.yaml' file. "
         "Use 'dandi download' to download a dandiset first."
     )