Remove pre-2013 vendor-prefixed -o- CSS properties

Summary:
Per https://caniuse.com/ and MDN,

• -o-animation superseded by unprefixed animation supported initially since Opera 12.1 released 11/2012, in later Opera versions with -webkit- prefix instead
• @-o-keyframes superseded by unprefixed @keyframes supported initially since Opera 12.1 released 11/2012, in later Opera versions with -webkit- prefix instead
• -o-transform superseded by unprefixed transform supported initially since Opera 12.1 released 11/2012
• -o-transition superseded by unprefixed transition supported initially since Opera 12.1 released 11/2012

Test Plan: None. Probably installing old browser versions if you don't trust documentation.

Reviewers: O1 Blessed Committers, valerio.bozzolan

Reviewed By: O1 Blessed Committers, valerio.bozzolan

Subscribers: tobiaswiese, valerio.bozzolan, Matthew, Cigaryno

Differential Revision: https://we.phorge.it/D25916