Update OptogeneticSeries to allow 2D data

[rly]

Motivation

Corresponds to schema changes in NeurodataWithoutBorders/nwb-schema#564

Checklist

• Did you update CHANGELOG.md with your changes?
• Have you checked our Contributing document?
• Have you ensured the PR clearly describes the problem and the solution?
• Is your contribution compliant with our coding style? This can be checked running flake8 from the source directory.
• Have you checked to ensure that there aren't other open Pull Requests for the same change?
• Have you included the relevant issue number using "Fix #XXX" notation where XXX is the issue number? By including "Fix #XXX" you allow GitHub to close issue #XXX when the PR is merged.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (5be83b6) 91.99% compared to head (ccc4538) 91.99%.

Additional details and impacted files

@@                Coverage Diff                @@
##           nwb-schema-2.7.0    #1812   +/-   ##
=================================================
  Coverage             91.99%   91.99%           
=================================================
  Files                    27       27           
  Lines                  2623     2623           
  Branches                685      685           
=================================================
  Hits                   2413     2413           
  Misses                  138      138           
  Partials                 72       72           

Flag	Coverage Δ
integration	71.10% <ø> (ø)
unit	83.68% <ø> (ø)

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