Transforms entry should mention lack of 3D support in IE9

[Fyrd]

Currently the entry mentions "3D space" and claims prefixed support starts in IE9, though IE9 only supports 2D transforms. Would be good to clarify that as someone suggested caniuse data was incorrect, citing this page.

[dstorey]

@jacobrossi what do you want to do about this? Just remove IE9 from prefixed? It seems from the text it is talking more about 3d transforms than 2d transforms (although now they're in the same spec)

[mattwojo]

@dstorey -- we are working on moving and updating Edge Dev Guide pages to the portal, just started on Transforms and saw this issue note. I believe you have access to our drafts, mind taking a look at the top note to see if this accurately represents support: https://github.com/MicrosoftEdge/MicrosoftEdge-Documentation-Private/blob/master/dev-guide/css/transforms/README.md