chore(deps): update dependency lerna to v3.21.0

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
lerna	devDependencies	minor	3.20.2 -> 3.21.0

---

Release Notes

lerna/lerna

### [`v3.21.0`](https://togithub.com/lerna/lerna/blob/master/CHANGELOG.md#​3210-httpsgithubcomlernalernacomparev3202v3210-2020-05-13) [Compare Source](https://togithub.com/lerna/lerna/compare/v3.20.2...v3.21.0) ##### Bug Fixes - **publish:** Canary releases without previous tags should not explode ([c9eb590](https://togithub.com/lerna/lerna/commit/c9eb590bf867889a188598322bb4552db7a34dfc)) ##### Features - **project:** Add `getPackagesSync()` export ([068bdd7](https://togithub.com/lerna/lerna/commit/068bdd75683ca9687a420523e4ba007bd8b3b220)) - **version:** Ignore private packages completely with `--no-private` ([a9b9f97](https://togithub.com/lerna/lerna/commit/a9b9f97457e4e4b0cac7f4ce562458d921a1f9be)) #### [3.20.2](https://togithub.com/lerna/lerna/compare/v3.20.1...v3.20.2) (2020-01-02) ##### Bug Fixes - **version:** Loosen `--atomic` fallback to catch incompatible CLI versions ([6f0e2bb](https://togithub.com/lerna/lerna/commit/6f0e2bb1b033b0579910cedcf0be84f1474c1580)), closes [#​2400](https://togithub.com/lerna/lerna/issues/2400) #### [3.20.1](https://togithub.com/lerna/lerna/compare/v3.20.0...v3.20.1) (2019-12-29) ##### Bug Fixes - **version:** Support git clients that do not support `git push --atomic` ([2b9b210](https://togithub.com/lerna/lerna/commit/2b9b210c0b6ac69853ffb01f0dbac9109ab419c5))

---

Renovate configuration

:date: Schedule: "every weekend" in timezone America/Los_Angeles.

:vertical_traffic_light: Automerge: Enabled.

:recycle: Rebasing: Whenever PR is behind base branch, or you tick the rebase/retry checkbox.

:no_bell: Ignore: Close this PR and you won't be reminded about this update again.

---

• [ ] If you want to rebase/retry this PR, check this box

---

This PR has been generated by WhiteSource Renovate. View repository job log here.