fix: fix dashboard model errors, change deprecated pytest function

[Wonong]

Summary of Changes

• Since the assertEquals function has been deprecated, replaced it with the assertEqual function for all test files.
• tests/unit/api/dashboard/fixture.py: Add chart_names field to dashboard fixture since model changes in amundsencommon

Tests

Passed all existing unit tests

Documentation

pytest doc about deprecated function: https://docs.python.org/3.3/library/unittest.html#deprecated-aliases
model changes in amundsencommon: https://github.com/amundsen-io/amundsencommon/pull/73/files

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[feng-tao]

thanks!