Update AnimGroupTemplate to match new constructor style
Update AnimGroupTemplate to match new constructor style

Also remove completeProperties since it is no longer needed

web-animations/web-animations-js-legacy,birtles/web-animations-js,birtles/web-animations-js,beni55/web-animations-js-legacy,dstockwell/web-animations-js,shans/web-anim-js,birtles/web-animations-js,beni55/web-animations-js-legacy,web-animations/web-animations-js-legacy,web-animations/web-animations-js-legacy,beni55/web-animations-js-legacy,dstockwell/web-animations-js,beni55/web-animations-js-legacy