Fix a broken link in the node js client sdk docs.

[roberthbailey]

It was missing a closing parenthesis.

[agones-bot]

Build Succeeded 👏

Build Id: d5ddcfa7-42ec-425b-9ba1-794159063175

The following development artifacts have been built, and will exist for the next 30 days:

• image: gcr.io/agones-images/agones-controller:1.0.0-9b1bd22
• image: gcr.io/agones-images/agones-sdk:1.0.0-9b1bd22
• image: gcr.io/agones-images/agones-ping:1.0.0-9b1bd22
• Linux C++ SDK (build): agonessdk-1.0.0-9b1bd22-linux-arch_64.tar.gz
• SDK Server: agonessdk-server-1.0.0-9b1bd22.zip

A preview of the website (the last 30 builds are retained):

• https://9b1bd22-dot-preview-dot-agones-images.appspot.com/

To install this version:

• git fetch https://github.com/GoogleCloudPlatform/agones.git pull/1045/head:pr_1045 && git checkout pr_1045
• helm install install/helm/agones --namespace agones-system --name agones --set agones.image.tag=1.0.0-9b1bd22

[google-oss-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: markmandel, roberthbailey
To complete the pull request process, please assign
You can assign the PR to them by writing /assign in a comment when ready.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment