Removed partial support for Android 4.0 and 4.1

As per the spec, http://www.w3.org/TR/2011/WD-html5-20110525/number-state.html, The placeholder attribute must not be specified and do not apply to the number input type. So, although Chrome did "fix" this quirk, it doesn't not make 4.0, 4.1 and webview buggy.