Update dependency mongoose to v5.12.4

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
mongoose (source)	5.12.3 -> 5.12.4

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Release Notes

Automattic/mongoose

### [`v5.12.4`](https://togithub.com/Automattic/mongoose/blob/master/History.md#​5124--2021-04-15) [Compare Source](https://togithub.com/Automattic/mongoose/compare/5.12.3...5.12.4) =================== - fix: upgrade mongodb driver -> 3.6.6 [#​10079](https://togithub.com/Automattic/mongoose/issues/10079) - fix: store fields set with select:false at schema-level when saving a new document [#​10101](https://togithub.com/Automattic/mongoose/issues/10101) [ptantiku](https://togithub.com/ptantiku) - fix(populate): avoid turning already populated field to null when populating an existing lean document [#​10068](https://togithub.com/Automattic/mongoose/issues/10068) [IslandRhythms](https://togithub.com/IslandRhythms) - fix(populate): correctly populate lean subdocs with `_id` property [#​10069](https://togithub.com/Automattic/mongoose/issues/10069) - fix(model): insertedDocs may contain docs that weren't inserted [#​10098](https://togithub.com/Automattic/mongoose/issues/10098) [olnazx](https://togithub.com/olnazx) - fix(schemaType): make type Mixed cast error objects to pojos [#​10131](https://togithub.com/Automattic/mongoose/issues/10131) [AbdelrahmanHafez](https://togithub.com/AbdelrahmanHafez) - fix(populate): support populating embedded discriminators in nested arrays [#​9984](https://togithub.com/Automattic/mongoose/issues/9984) - fix(populate): handle populating map paths using trailing `.$*` [#​10123](https://togithub.com/Automattic/mongoose/issues/10123) - fix(populate): allow returning primitive from `transform()` function for single conventional populate [#​10064](https://togithub.com/Automattic/mongoose/issues/10064) - fix(index.d.ts): allow generic classes of `T` to use `T & Document` internally [#​10046](https://togithub.com/Automattic/mongoose/issues/10046) - fix(index.d.ts): allow `$pull` with `$` paths [#​10075](https://togithub.com/Automattic/mongoose/issues/10075) - fix(index.d.ts): use correct `Date` type for `$currentDate` [#​10058](https://togithub.com/Automattic/mongoose/issues/10058) - fix(index.d.ts): add missing asyncInterator to Query type def [#​10094](https://togithub.com/Automattic/mongoose/issues/10094) [borfig](https://togithub.com/borfig) - fix(index.d.ts): allow RHS of `$unset` properties to be any value [#​10066](https://togithub.com/Automattic/mongoose/issues/10066) - fix(index.d.ts): allow setting SchemaType `index` property to a string [#​10077](https://togithub.com/Automattic/mongoose/issues/10077) - refactor(index.d.ts): move discriminator() to common interface [#​10109](https://togithub.com/Automattic/mongoose/issues/10109) [LoneRifle](https://togithub.com/LoneRifle)

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