[Bug]: Validator incorrectly reads datetime-formatted string as isodatetime when spec dtype is string

[rly]

What happened?

See NeurodataWithoutBorders/pynwb#1819

This happens in https://github.com/hdmf-dev/hdmf/blob/dev/src/hdmf/validate/validator.py#L105-L107

Steps to Reproduce

# using pynwb
from pynwb.testing.mock.file import mock_NWBFile
from pynwb import NWBHDF5IO

with NWBHDF5IO(path=".../Downloads/test_invalid.nwb.hdf5", mode="w") as io:
    io.write(mock_NWBFile(session_id="2024-01-01"))

Traceback

- found the following errors:
root/general/session_id (general/session_id): incorrect type - expected 'text', got 'isodatetime'

Operating System

Windows

Python Executable

Conda

Python Version

3.11

Package Versions

No response