Make CSS length unit descriptions consistent

features/cap.yml

@@ -1,4 +1,4 @@
 name: cap unit
-description: The CSS `cap` unit corresponds to the height of Latin capital letters.
+description: The `cap` CSS length unit corresponds to the height of Latin capital letters.
 spec: https://drafts.csswg.org/css-values-4/#cap
 group: units

features/ic.yml

@@ -1,4 +1,4 @@
 name: ic unit
-description: The CSS `ic` unit corresponds to the width of CJK ideographic characters.
+description: The `ic` CSS length unit corresponds to the width of CJK ideographic characters.
 spec: https://drafts.csswg.org/css-values-4/#ic
 group: units

features/lh.yml

@@ -1,4 +1,4 @@
 name: lh unit
-description: The CSS `lh` unit corresponds to the requested line height, the computed value of the `line-height` property. Some lines may be higher than this based on their content.
+description: The `lh` CSS length unit corresponds to the requested line height, the computed value of the `line-height` property. Some lines may be higher than this based on their content.
 spec: https://drafts.csswg.org/css-values-4/#lh
 group: units