JS client: fixed syntax error in npm readme

[Ymirke]

Description of changes

Incorrect comma, should have been a colon.

Summarize the changes made by this PR.

• Improvements & Bug fixes
  - No bug fixes
• New functionality
  • No new functionality

Test plan

How are these changes tested?
No functionality changes

Documentation Changes

Are all docstrings for user-facing APIs updated if required? Do we need to make documentation changes in the docs repository?

Incorrect comma, should have been a colon.

[github-actions]

Reviewer Checklist

Please leverage this checklist to ensure your code review is thorough before approving

Testing, Bugs, Errors, Logs, Documentation

• Can you think of any use case in which the code does not behave as intended? Have they been tested?
• Can you think of any inputs or external events that could break the code? Is user input validated and safe? Have they been tested?
• If appropriate, are there adequate property based tests?
• If appropriate, are there adequate unit tests?
• Should any logging, debugging, tracing information be added or removed?
• Are error messages user-friendly?
• Have all documentation changes needed been made?
• Have all non-obvious changes been commented?

System Compatibility

• Are there any potential impacts on other parts of the system or backward compatibility?
• Does this change intersect with any items on our roadmap, and if so, is there a plan for fitting them together?

Quality

• Is this code of a unexpectedly high quality (Readbility, Modularity, Intuitiveness)

[jeffchuber]

thank you!