Mark Edge 79 as not obsolete again (compat-table#1587)

Author: chicoxyzzy

environments.json

@@ -2242,9 +2242,10 @@
     "full": "Microsoft Edge 79",
     "family": "V8",
     "release": "2020-01-15",
+    "retire": "2020-02-07",
     "short": "Edge 79",
     "equals": "chrome79",
-    "obsolete": true
+    "obsolete": false
   },
   "edge80": {
     "full": "Microsoft Edge 80",