Correct typo in documentation

corrected homonym error.
Merge pull request #2447 from lazaruslarue/patch-1

Correct documentation typo.
Delegate transformation to `ol.format.*`

Fixes #2604.
Merge pull request #2662 from gingerik/delegate-transformation

Delegate transformation in ol.source.FormatVector#readFeatures to `ol.format.*`
Add olx.layer.ImageOptions typedef
Set ol.layer.Image#getSource return type to ol.source.Image
Remove unnecessary type cast
Set ol.layer.Tile#getSource return type to ol.source.Tile
Remove unnecessary type cast
Don't expose olx.layer.LayerOptions
Don't expose olx.layer.BaseOptions