Fix typo and remove trailing whitespace in slice.rs
@@ -121,7 +121,7 @@ impl<R: Resources> Slice<R> {
/// Type of index-buffer used in a Slice.
///
/// The `Auto` variant represents a hypothetical index-buffer from 0 to infinity. In other words,
-/// all vertices get processed in order. Do note that the `Slice`' `start` and `end` restrictions
+/// all vertices get processed in order. Do note that the `Slice`'s `start` and `end` restrictions
/// still apply for this variant. To render every vertex in the `VertexBuffer`, you would set
/// `start` to 0, and `end` to the `VertexBuffer`'s length.
///
