Clarify LabMetaData guidance: discourage one-row DynamicTable usage

[Copilot]

The LabMetaData extension tutorial note could be read as recommending DynamicTable for simple extended metadata, including single-record cases. This update tightens the wording to distinguish tabular metadata from simple lab metadata and prevent that misinterpretation.

• What was clarified

  • Kept the existing examples of valid DynamicTable use (TimeIntervals, ElectrodeTable).
  • Added explicit guidance that DynamicTable is appropriate when metadata is naturally tabular (multiple similar records/rows).

• What was discouraged

  • Explicitly discourages creating a one-row DynamicTable for simple, non-tabular lab metadata.

• Recommended path for this use case

  • Directs users to define a LabMetaData extension with explicit fields for simple lab-specific metadata.

Use these table structures when your metadata are naturally tabular (i.e., multiple rows of similar records).
For simple lab-specific metadata that are not tabular, avoid creating a one-row ``DynamicTable`` and
instead define a :py:class:`~pynwb.file.LabMetaData` extension with explicit fields as shown below.