[caffe2] don't use static for template declarations in headers (#53602)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/53602
Using static in headers causes code bloat. Remove the unnecessary `static` qualifiers.
Test Plan: sandcastle
Reviewed By: asp2insp
Differential Revision: D26886180
fbshipit-source-id: 6008bce0d47f06d3146ce998234574a607c99311
