fix: added graphviz to build packages

[peterkomar-aws]

Issue #, if available:
Documentation (https://amazon-braket-pennylane-plugin-python.readthedocs.io/en/latest/code.html#class-inheritance-diagram) does not display the graph.

Description of changes:
Based on this successful PR on the Pennylan repo (PennyLaneAI/pennylane#4284), I am adding graphviz package to build environment to create.

Testing done:

I was not able to test it, because I don't have dot installed on my machine. Please help.

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[peterkomar-aws]

I run tox -e docs to build the documentation locally, but I received this warning that seemed relevant:

WARNING: dot command 'dot' cannot be run (needed for graphviz output), check the graphviz_dot setting

And the page at amazon-braket-pennylane-plugin-python/build/documentation/html/code.html still does not show the graph.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (21e21c6) to head (e7ba647).
⚠️ Report is 16 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #209   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            7         7           
  Lines         1256      1256           
  Branches       179       179           
=========================================
  Hits          1256      1256           

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[AbeCoull]

Would using the graphviz plugin work for this?