TL;DR: it’s fine, don’t worry about it.
Why
Figma uses its own font rendering because each device renders fonts differently depending on the device, OS type and version, browser and its version, system settings, browser settings, display and maybe some other factors. Figma has to use one font rendering for all because it’s a collaborative tool with one source of truth.
What to do
It is the current reality of the web that fonts render differently for everyone. There is nothing you can do about it. Yes, your font differs from Figma, but it would also be different for every user who visits your website. You can even be thankful that you got noticeable difference from Figma because it’s a reminder that everyone will be seeing your website in a different way.