Remove query_params explicity conversion to dict

[umr55766]

• This explicit conversion to dict is dropping all the values with same key
• This is already being done in line 169 https://github.com/aschn/drf-tracking/blob/57344c65fe39923ab2debbf581d9fd0dbc46b2fa/rest_framework_tracking/base_mixins.py#L169
• Fixes #126

[avelis]

@umr55766 Can you address the failing tests before I take a look?

[simone6021]

@umr55766, i looked into failing tests and i think they should include client calls with different content_type:

• 'multipart' (default in drf tests) which will return lists
• 'json' which is expected to have single string values