remove useless argument of ScreenSpaceEventHandler

[bbbbx]

see https://groups.google.com/forum/?hl=en#!topic/cesium-dev/huOer7E71Iw for details

[cesium-concierge]

Thank you so much for the pull request @bbbbx! I noticed this is your first pull request and I wanted to say welcome to the Cesium community!

The Pull Request Guidelines is a handy reference for making sure your PR gets accepted quickly, so make sure to skim that.

• ❌ Missing CONTRIBUTORS.md entry.
  • Please add yourself to the contributors file!
• ❌ Missing CLA.
  • Please send in a Contributor License Agreement (CLA) and comment back here to let us know to check this!
• ❔ CHANGES.md was not updated.
  • If this change updates the public API in any way, please add a bullet point to CHANGES.md.
• ❔ Unit tests were not updated.
  • Make sure you've updated tests to reflect your changes, added tests for any new code, and ran the code coverage tool.

Reviewers, don't forget to make sure that:

• Cesium Viewer works.
• Works in 2D/CV.
• Works (or fails gracefully) in IE11.

[bbbbx]

I have signed the CLA.

[hpinkos]

@OmarShehata have we received a CLA?

[OmarShehata]

@hpinkos yes, CLA is signed!

[hpinkos]

Thanks for the contribution @bbbbx !

[cesium-concierge]

Congratulations on closing the issue! I found these Cesium forum links in the comments above:

https://groups.google.com/forum/?hl=en#!topic/cesium-dev/huOer7E71Iw](https

If this issue affects any of these threads, please post a comment like the following:

The issue at #8160 has just been closed and may resolve your issue. Look for the change in the next stable release of Cesium or get it now in the master branch on GitHub https://github.com/AnalyticalGraphicsInc/cesium.