Disable deprecated filters by default

[cwjohnston]

Description

• Remove logic for disabling deprecated filters via global override
• Update logic to ensure deprecated filters are disabled by default

Motivation and Context

As described in #134, this change is part of a strategy to move event filtering out of this library and into Sensu Core.

How Has This Been Tested?

Updated unit tests to test the new desired behavior.

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [x] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [x] My change requires a change to the documentation.
• [x] I have updated the documentation accordingly.
• [x] I have updated the Changelog following the conventions laid out on Keep A Changelog

Known Caveats

Requires a major version bump in order to follow SemVer.

[portertech]