revert context.hook_data data type to dict

[ITProKyle]

Why This Is Needed

To support legacy uses that do not handle MutableMap until we can enforce the breaking change in the next major release.

Blueprint use case that was broken:

        ...
        template.add_resource(ssm.Document(
            'SsmDocument',
            Content=self.context.hook_data['json']],
            DocumentType='Command'
        ))

Which resulted in the following error.

ERROR:runway.cfngin.plan:<class 'troposphere.ssm.Document'>: SsmDocument.Content is <class 'runway.util.MutableMap'>, expected <class 'dict'>

What Changed

Fixed

• cfngin hook_data is once again stored as a dict rather than MutableMap to support stacker hooks/lookups/blueprints that do not handle the MutableMap data type when consuming hook_data.