How to remove chrome app icons from launchpad?
Open Finder, select Go/Go to Folder... (⇧⌘G), paste in:

~/Applications/Chrome Apps.localized


Delete the apps from there.

(Note that ~ means your user folder, not the regular Applications folder which is at /Applications without ~.)

Finally, empty the trash to remove from launchpad.

If you use Chrome Canary: it will have its own additional folder in ~/Applications.