Fix `length-percentage> description

Author: caugner

css/types/attr.json

@@ -385,7 +385,7 @@
           },
           "length-percentage": {
             "__compat": {
-              "description": "`<length>`",
+              "description": "`<length-percentage>`",
               "mdn_url": "https://developer.mozilla.org/docs/Web/CSS/Reference/Values/length-percentage",
               "spec_url": "https://drafts.csswg.org/css-values/#mixed-percentages",
               "tags": [