As TImeline visual: remove borders

I am using an As Timeline in my visual to give an overview of when a user was active, any gaps in the chart show when a user was inactive. Each activity has it's own entry so there are hundreds of entries, and therefore hundreds of individuals timeline bars.

Here's a screenshot of my visual:

So my problem is that there these ugly borders that I am looking to get rid of, so that there are continuous blue bars. I have access to the .json file but have no knowledge in this language so am unsure of where to look to edit this?

Thanks,

Morgan