▶ symbol gets replaced by image

Hi,
For some reason, whenever I add a ▶ symbol to a page or post WordPress changes it into an image. More specifically, it changes the symbol into this whole bit of code:

<img src="https://s.w.org/images/core/emoji/72x72/25b6.png" alt="▶" class="emoji" draggable="false">

Does anyone know what’s causing this and how to remove it so that just the unicode icon shows up? I can’t seem to find anything related to this change and the issue is ‘un-Googleable’ since symbols like this one are not detected in the searchbar.