Fix missing web-animations.html

This was not updated when web-animations-next changed their naming scheme. I am not sure if this is the right file, there are several:
web-animations.dev.html
web-animations-next.dev.html
web-animations-next-lite.dev.html

This 0.5 release was a messy one. Do you guys need any help? I keep telling people that Polymer is the future. I am 5 mins away from your campus. I know plently of Googlers, but no one on Polymer team, asking you this in a pull might spare me digging through my contact list.