Fixed bad source default

[colin99d]

Description

Fixes #2579

The source was defaulting to yahoo finance, which was not returning results. The API does not require a source, so for now I always send None. I personally do not see the value of being able to set the source, but if others feel its necessary I can add a parser argument. Users can still set the source in the API.

How has this been tested?

Ran command in terminal and api, ran pytest

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