The edit did exist. So the phrase "Multiple studies have found a left-wing bias at Wikipedia" can be found last in the edit (4 February 2025) [1] and was removed by the editor Aquillion with the explanation [2]

     Not seeing anything in this source that supports this language; they summarize no other sources that I could see, and their own conclusions are more complex than this (as covered further down the article.)

[1] https://en.wikipedia.org/w/index.php?title=Ideological_bias_...

[2] https://en.wikipedia.org/w/index.php?title=Ideological_bias_...

I am not surprised that the sentence existed once. But "Wikipedia once said this during the time August 2024-Februrary 2025" is not the same as "Source: Wikipedia" because of the way Wikipedia evolves. It's especially bad if you disregard the entire much more nuanced discussion in the remaining article.