Docs: Gateron Chocolate Switch Spring Spec

There’s a missing stat for the Gateron spring action on the table in:

https://github.com/ergonautkb/ergonautkb.github.io/blob/main/docs/switches/gateron-low-profile.md

It can be listed as:

“13.5mm double-stage spring“

Taken from the infographics halfway down here:

https://www.gateron.com/products/gateron-ks-33-low-profile-20-chocolate-switch?VariantsId=11139