Don't need the checkbox; the hook does it

Reviewed-by: NKurt Roeckx <kurt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/2317)

.github/PULL_REQUEST_TEMPLATE.md

@@ -8,7 +8,6 @@ Contributors guide: https://github.com/openssl/openssl/blob/master/CONTRIBUTING
 <!-- Remove items that do not apply. For completed items, change [ ] to [x]. -->
 - [ ] documentation is added or updated
 - [ ] tests are added or updated
-- [ ] CLA is signed
 
 ##### Description of change
 <!-- Provide a description of the changes.