Upgrade hashdiff

[vivekbisen]

What

See title ☝️

Why

> opsicle --version
The HashDiff constant used by this gem conflicts with another gem of a similar name.  As of version 1.0 the HashDiff constant will be completely removed and replaced by Hashdiff.  For more information see https://github.com/liufengyun/hashdiff/issues/45.
opsicle version 2.13.1

Deploy Plan

Does Platform Operations need to know anything special about this deploy? Are migrations present?

Rollback Plan

• To roll back this change, revert the merge with: git revert -m 1 MERGE_SHA and perform another deploy.

URLs

Links to bug tickets or user stories.

QA Plan

• Checkout the branch.
• Build the gem locally.
• Run opsicle --version or any other opsicle command.
• Verify that the deprecation warning is gone and command works as expected.

[mpillsbury]

Wait—I changed my mind. There are failing tests that still reference the old HashDiff constant.

[production-status-check]

Has QA approval