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/properties/longhands/padding.mako.rs

@@ -16,10 +16,10 @@
     %>
     ${helpers.predefined_type(
         "padding-%s" % side[0],
-        "NonNegativeLengthOrPercentage",
-        "computed::NonNegativeLengthOrPercentage::zero()",
+        "NonNegativeLengthPercentage",
+        "computed::NonNegativeLengthPercentage::zero()",
         alias=maybe_moz_logical_alias(product, side, "-moz-padding-%s"),
-        animation_value_type="NonNegativeLengthOrPercentage",
+        animation_value_type="NonNegativeLengthPercentage",
         logical=side[1],
         logical_group="padding",
         spec=spec,