Update Edge data for backdrop-filter

https://caniuse.com/css-backdrop-filter has a note for Edge 17-18 which
turns out to be correct. It was only supported as
-webkit-backdrop-filter, presumably due to site compat issues.

This was verified by testing https://wpt.live/css/filter-effects/backdrop-filter-basic.html
in Edge 17. The test doesn't pass as-is, but changing backdrop-filter to
-webkit-backdrop-filter and it does render as expected.

css/properties/backdrop-filter.json

@@ -10,9 +10,16 @@
  "version_added": "76"
  },
  "chrome_android": "mirror",
- "edge": {
- "version_added": "17"
- },
+ "edge": [
+ {
+ "version_added": "79"
+ },
+ {
+ "prefix": "-webkit-",
+ "version_added": "17",
+ "version_removed": "79"
+ }
+ ],
  "firefox": {
  "version_added": "103"
  },