style: Rename LengthOrPercentage to LengthPercentage.

It does not represent `<length> | <percentage>`, but `<length-percentage>`, so
`LengthOrPercentage` is not the right name.

This patch is totally autogenerated using:

rg 'LengthOrPercentage' servo | cut -d : -f 1 | sort | uniq > files
for file in $(cat files); do sed -i "s#LengthOrPercentage#LengthPercentage#g" $file; done

Differential Revision: https://phabricator.services.mozilla.com/D15812

components/style/values/generics/gecko.rs

@@ -8,12 +8,12 @@
 /// A generic value for scroll snap points.
 #[cfg_attr(feature = "gecko", derive(MallocSizeOf))]
 #[derive(Clone, Copy, Debug, PartialEq, SpecifiedValueInfo, ToComputedValue, ToCss)]
-pub enum ScrollSnapPoint<LengthOrPercentage> {
+pub enum ScrollSnapPoint<LengthPercentage> {
     /// `none`
     None,
     /// `repeat(<length-or-percentage>)`
     #[css(function)]
-    Repeat(LengthOrPercentage),
+    Repeat(LengthPercentage),
 }
 
 impl<L> ScrollSnapPoint<L> {