Chrome 143 supports side-relative values for background-position-x/y (#28494)

* Chrome 143 supports side-relative values for `background-position-x/y`

e.g.

```css
.test {
  background-position-x: left 25%;
  background-position-y: top 30px;
}
```

https://chromestatus.com/feature/5073321259565056

* Apply suggestions from code review

---------

Co-authored-by: Claas Augner <[email protected]>

Author: yisibl

css/properties/background-position-x.json

@@ -42,13 +42,13 @@
         },
         "side-relative_values": {
           "__compat": {
-            "description": "Side-relative values (such as `bottom 10%`)",
+            "description": "Side-relative values (such as `left 10%`)",
             "tags": [
               "web-features:background-position"
             ],
             "support": {
               "chrome": {
-                "version_added": false
+                "version_added": "143"
               },
               "chrome_android": "mirror",
               "edge": {

css/properties/background-position-y.json

@@ -48,7 +48,7 @@
             ],
             "support": {
               "chrome": {
-                "version_added": false
+                "version_added": "143"
               },
               "chrome_android": "mirror",
               "edge": {