Clean up two more sha1 instances

Summary: See T547. One of these I just missed in D1000; the comment change just
makes it easier to audit use of hash functions by cleaning up "grep" output.

Test Plan: Ran isolation unit test.

Reviewers: btrahan, jungejason, nh, tuomaspelkonen, aran

Reviewed By: jungejason

CC: aran, jungejason

Differential Revision: 1124