devel/git-lfs: update 2.6.0 to 2.6.1

• git: close blob objects when finished;
• Avoid hang in repos cloned with --shared or --reference;
• vendor: don't remove necessary dependencies.

https://raw.githubusercontent.com/git-lfs/git-lfs/v2.6.1/CHANGELOG.md

Approved by: araujo (mentor)
Differential Revision: https://reviews.freebsd.org/D18446