Update css-anchor-positioning.json (#7030)

Anchor positioning shipping in 125: https://chromestatus.com/feature/5124922471874560

Author: soluml

features-json/css-anchor-positioning.json

@@ -341,8 +341,8 @@
       "122":"n d #1",
       "123":"n d #1",
       "124":"n d #1",
-      "125":"n d #1",
-      "126":"n d #1"
+      "125":"y",
+      "126":"y"
     },
     "safari":{
       "3.1":"n",