elasticsearch: Fix indexing blobs and commits with strict mapping on

What does this MR do?

The elasticsearch index recently gained strict, rather than dynamic, mapping. However, we're still missing two important fields:

• repository.commit.type
• repository.blob.type

I mistakenly thought all was well, when in fact our Ruby and Go indexers both silently ignore documents that fail to create. gitlab-elasticsearch-indexer#28 (closed) is a follow-up issue for that problem.

This fix is sufficient to bring the document count back up to the right number on my test instance (~262,000 instead of ~2000)

What are the relevant issue numbers?

Regression introduced in https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/9760

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated via this MR
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• EE specific content should be in the top level /ee folder
• For a paid feature, have we considered GitLab.com plans, how it works for groups, and is there a design for promoting it to users who aren't on the correct plan?
• Security reports checked/validated by reviewer

cc @mdelaossa