functions: remove kafka-node dependency (#1418)

Author: chriso

src/_includes/content/functions/runtime.md

@@ -16,7 +16,6 @@ The following dependencies are installed in the function environment by default.
 - [`@google-cloud/pubsub v2.6.0`](https://www.npmjs.com/package/@google-cloud/pubsub) exposed as `google.cloud.pubsub`
 - [`@google-cloud/storage v5.3.0`](https://www.npmjs.com/package/@google-cloud/storage) exposed as `google.cloud.storage`
 - [`jsonwebtoken v8.5.1`](https://www.npmjs.com/package/jsonwebtoken) exposed as `jsonwebtoken`
-- [`kafka-node v5.0.0`](https://www.npmjs.com/package/kafka-node) exposed as `kafka-node`
 - [`lodash v4.17.15`](https://www.npmjs.com/package/lodash) exposed as `_`
 - [`node-fetch v2.6.0`](https://www.npmjs.com/package/node-fetch) exposed as `fetch`
 - [`oauth v0.9.15`](https://www.npmjs.com/package/oauth) exposed as `OAuth`