Deprecate EventWaveform class

[rly]

Motivation

Corresponds to NeurodataWithoutBorders/nwb-schema#584

• Waiting on test suite to pass
• Waiting on schema changes to merge to dev

How to test the behavior?

EventWaveform()  # should return a ValueError

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 ruff check . && codespell 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

Attention: Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review.

Please upload report for BASE (nwb_schema_2.8.0@f89ce99). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
src/pynwb/ecephys.py	66.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@                 Coverage Diff                 @@
##             nwb_schema_2.8.0    #1940   +/-   ##
===================================================
  Coverage                    ?   92.02%           
===================================================
  Files                       ?       27           
  Lines                       ?     2709           
  Branches                    ?      706           
===================================================
  Hits                        ?     2493           
  Misses                      ?      141           
  Partials                    ?       75           

Flag	Coverage Δ
integration	72.90% <33.33%> (?)
unit	82.98% <66.66%> (?)

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[rly]

I accidentally updated the changelog in the nwb_schema_2.8.0 branch. I think we can move forward with this commit to that branch.