fix(deps): update dependency symbol-observable to v3

[mesosphere-renovate]

This PR contains the following updates:

Package	Type	Update	Change
symbol-observable	dependencies	major	2.0.3 -> 3.0.0

---

Release Notes

blesh/symbol-observable

### [`v3.0.0`](https://togithub.com/blesh/symbol-observable/blob/master/CHANGELOG.md#​300httpsgithubcombleshsymbol-observablecompare203300-2020-11-02) [Compare Source](https://togithub.com/blesh/symbol-observable/compare/2.0.3...6b9ca7f1891b0e79170299dc071a6ad923afb5d3) ##### Bug Fixes - **TypeScript:** `Symbol.observable` is now `unique symbol`. ([2ef1476](https://togithub.com/blesh/symbol-observable/commit/2ef147644cf78538b28c3fd9e66a3b8d569a1978)), closes [#​41](https://togithub.com/blesh/symbol-observable/issues/41) - **TypeScript:** `Symbol[Symbol.observable]` is no longer incorrectly defined ([fe4301f](https://togithub.com/blesh/symbol-observable/commit/fe4301f37b54162e1a2db91e79c5b33d652496f1)) ##### BREAKING CHANGES - **TypeScript:** Older versions of `@types/node` will clash with this, because `@types/node` incorrectly defined `Symbol.observable` has `symbol` and not `unique symbol`. Update to `@types/node@14.14.6` or higher. #### [2.0.3](https://togithub.com/blesh/symbol-observable/compare/2.0.2...2.0.3) (2020-09-30) ##### Bug Fixes - **package.json** ponyfill.d.ts added to package ([b25f5bf](https://togithub.com/blesh/symbol-observable/commit/b25f5bfe7425ad21f510428795de8b38aee70b2e)) #### [2.0.2](https://togithub.com/blesh/symbol-observable/compare/2.0.1...2.0.2) (2020-09-29) ##### Bug Fixes - **TypeScript** ponyfill types added ([10d2ec8](https://togithub.com/blesh/symbol-observable/commit/10d2ec8f0809ac9134be91378fc45c3578f675d4)) #### [2.0.1](https://togithub.com/blesh/symbol-observable/compare/2.0.0...2.0.1) (2020-09-04) ##### Bug Fixes - **package.json:** es/ponyfill.js no longer typoed ([ad2c079](https://togithub.com/blesh/symbol-observable/commit/ad2c079c71536eaf972101a25eb18f5bca94ab62)) - Resolve issues in environments with frozen Symbol ([2323882](https://togithub.com/blesh/symbol-observable/commit/23238827ea234188b11774f43afcb5c8deeb278e))

---

Renovate configuration

:date: Schedule: At any time (no schedule defined).

:vertical_traffic_light: Automerge: Disabled by config. Please merge this manually once you are satisfied.

:recycle: Rebasing: Whenever PR becomes conflicted, or if you modify the PR title to begin with "rebase!".

: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

---

Available now for Enterprise: Renovate Pro with real-time webhook handling and priority job queue.