I am trying to remove my ssl certificate so showit.co can apply their ssl. On my google domains "security" page it says that Let's Encrypt is the one connecting my current ssl cretificate.
Let's Encrypt is the Certificate Authority (CA) that issued the certificate. Once a certificate is issued, it is to be installed by the holder of that certificate, where "holder" usually is the person or organisation which requested the certificate from Let's Encrypt in the first place.
After issuance, Let's Encrypt doesn't "control" the certificate any longer, it's the holders responsibility to use it or to stop using it.
You don't have to remove a certificate to replace it with another.
There should be nothing stopping
showit.co from obtaining a certificate for, and applying a certificate to, your site.
Given that it is being hosted by them.
Think of it much like a cert renewal.
The new cert merely replaces the current one.
[which could be from another CA/provider]