Shaders: Remove workaround for Adreno bug

[WestLangley]

Related issue: #9988

Perhaps it's OK to remove this workaround circa 2016.

[WestLangley]

/ping @sunag If this is merged, similar changes can be made in Node.

[sunag]

/ping @sunag If this is merged, similar changes can be made in Node.

Yes... Thanks for let me know.

[Mugen87]

The workaround was added for Adreno 300 series and the respective Snapdragon SoCs are not used for new phones since a couple of years now. I think we can risk to remove it.

[mrdoob]

Thanks!

[Mugen87]

@WestLangley It seems we can also refactor the following now?

three.js/src/renderers/shaders/ShaderChunk/normal_fragment_begin.glsl.js

Lines 6 to 10 in d934606

	// Workaround for Adreno GPUs not able to do dFdx( vViewPosition )
	vec3 fdx = vec3( dFdx( vViewPosition.x ), dFdx( vViewPosition.y ), dFdx( vViewPosition.z ) );
	vec3 fdy = vec3( dFdy( vViewPosition.x ), dFdy( vViewPosition.y ), dFdy( vViewPosition.z ) );
	vec3 normal = normalize( cross( fdx, fdy ) );

[WestLangley]

@Mugen87 Good point! 👍