pubsub: Label pub sub client as experimental

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [sinon](https://sinonjs.org/) ([source](https://togithub.com/sinonjs/sinon)) | [`^10.0.0` -> `^11.0.0`](https://renovatebot.com/diffs/npm/sinon/10.0.0/11.1.0) | [![age](https://badges.renovateapi.com/packages/npm/sinon/11.1.0/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/npm/sinon/11.1.0/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/npm/sinon/11.1.0/compatibility-slim/10.0.0)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/npm/sinon/11.1.0/confidence-slim/10.0.0)](https://docs.renovatebot.com/merge-confidence/) |

---

### Release Notes

<details>
<summary>sinonjs/sinon</summary>

### [`v11.1.0`](https://togithub.com/sinonjs/sinon/blob/master/CHANGELOG.md#&#8203;1110--2021-05-25)

[Compare Source](https://togithub.com/sinonjs/sinon/compare/v11.0.0...31be9a5d5a4762ef01cb195f29024616dfee9ce8)

\==================

-   Add sinon.promise() implementation ([#&#8203;2369](https://togithub.com/sinonjs/sinon/issues/2369))
-   Set wrappedMethod on getters/setters ([#&#8203;2378](https://togithub.com/sinonjs/sinon/issues/2378))
-   \[Docs] Update fake-server usage & descriptions ([#&#8203;2365](https://togithub.com/sinonjs/sinon/issues/2365))
-   Fake docs improvement ([#&#8203;2360](https://togithub.com/sinonjs/sinon/issues/2360))
-   Update nise to 5.1.0 (fixed [#&#8203;2318](https://togithub.com/sinonjs/sinon/issues/2318))

### [`v11.0.0`](https://togithub.com/sinonjs/sinon/blob/master/CHANGELOG.md#&#8203;1100--2021-05-24)

[Compare Source](https://togithub.com/sinonjs/sinon/compare/v10.0.1...v11.0.0)

\==================

-   Explicitly use samsam 6.0.2 with fix for [#&#8203;2345](https://togithub.com/sinonjs/sinon/issues/2345)
-   Update most packages ([#&#8203;2371](https://togithub.com/sinonjs/sinon/issues/2371))
-   Update compatibility docs ([#&#8203;2366](https://togithub.com/sinonjs/sinon/issues/2366))
-   Update packages (includes breaking fake-timers change, see [#&#8203;2352](https://togithub.com/sinonjs/sinon/issues/2352))
-   Warn of potential memory leaks ([#&#8203;2357](https://togithub.com/sinonjs/sinon/issues/2357))
-   Fix clock test errors

### [`v10.0.1`](https://togithub.com/sinonjs/sinon/blob/master/CHANGELOG.md#&#8203;1001--2021-04-08)

[Compare Source](https://togithub.com/sinonjs/sinon/compare/v10.0.0...v10.0.1)

\==================

-   Upgrade sinon components (bumps y18n to 4.0.1)
-   Bump y18n from 4.0.0 to 4.0.1

</details>

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Resolves #69

…115)

Fix #114

Closes #115

Closes #115

Closes #115