Use mock apollo to test commit section mutation

The following discussion from !52790 (merged) should be addressed:

• @pburdette started a discussion: (+3 comments)

  Suggestion (non-blocking): This could be a followup issue, but I think we need to consider using mock-apollo client here. In the mutation if the data is ever destructed wrong (typo) this tests will still pass as is.

test that store.writeQuery({ query: getCommitSha, data: { commitSha } }); is properly called when we mutate