[Image] Remove resizeMode from nativeOnlyProps to get rid of warning

[brentvatne]

@chirag04 pointed out in irc that he was getting warnings about using the resizeMode prop on Image. My understanding is that it should be used as a prop, and that using it in the style was slated to be deprecated.

This pull request gets rid of the warning message above, but stops short of adding a warning when using resizeMode via style - I would like to continue and add that warning if you agree @vjeux

[chirag04]

@brentvatne Anything on this? Now that react-native 0.6 is released i see this warning all over my app. :(

[brentvatne]

@chirag04 - this is fixed in 0.7.0-rc actually: 4750856

I'd wait until we merge in a fix for #1750 before using that version though

[chirag04]

oh. Cool. Thanks.