Upgrade: Bump mongoose from 5.7.3 to 5.7.4

[dependabot-preview]

Bumps mongoose from 5.7.3 to 5.7.4.

Changelog

Sourced from mongoose's changelog.

5.7.4 / 2019-10-09

• fix(schema): handle required: null and required: undefined as required: false #8219
• fix(update): support updating array embedded discriminator props if discriminator key in $elemMatch #8063
• fix(populate): allow accessing populate virtual prop underneath array when virtual defined on top level #8198
• fix(model): support passing options to Model.remove() #8211
• fix(document): handle Document#set() merge option when setting underneath single nested schema #8201
• fix: use options constructor class for all schematypes #8012

Commits

• ede5aef chore: release 5.7.4
• 402db1a fix(model): support passing options to Model.remove()
• 7a20276 fix(schema): handle required: null and required: undefined as `required: ...
• 9b4a323 test(schema): repro #8219
• fb66f3a fix: use options constructor class for all schematypes
• d5e0c73 refactor: use options constructor for array, buffer, date schematypes re: #8012
• 2d0955d refactor: use SchemaNumberOptions class for schematype number re: #8012
• 166cd88 refactor: use SchemaStringOptions class for string schematype options re: #8012
• 523c181 fix(update): support updating array embedded discriminator props if discrimin...
• f277d94 test(update): repro #8063
• Additional commits viewable in compare view

Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. You can also trigger a rebase manually by commenting @dependabot rebase.

If all status checks pass Dependabot will automatically merge this pull request.

---

Dependabot commands and options

You can trigger Dependabot actions by commenting on this PR:

• @dependabot rebase will rebase this PR
• @dependabot recreate will recreate this PR, overwriting any edits that have been made to it
• @dependabot merge will merge this PR after your CI passes on it
• @dependabot squash and merge will squash and merge this PR after your CI passes on it
• @dependabot cancel merge will cancel a previously requested merge and block automerging
• @dependabot reopen will reopen this PR if it is closed
• @dependabot close will close this PR and stop Dependabot recreating it. You can achieve the same result by closing it manually
• @dependabot ignore this major version will close this PR and stop Dependabot creating any more for this major version (unless you reopen the PR or upgrade to it yourself)
• @dependabot ignore this minor version will close this PR and stop Dependabot creating any more for this minor version (unless you reopen the PR or upgrade to it yourself)
• @dependabot ignore this dependency will close this PR and stop Dependabot creating any more for this dependency (unless you reopen the PR or upgrade to it yourself)
• @dependabot badge me will comment on this PR with code to add a "Dependabot enabled" badge to your readme

Additionally, you can set the following in the .dependabot/config.yml file in this repo:

• Update frequency
• Automerge options (never/patch/minor, and dev/runtime dependencies)
• Out-of-range updates (receive only lockfile updates, if desired)
• Security updates (receive only security updates, if desired)