Update CONTRIBUTING.md (#6831)

* Update CONTRIBUTING.md

Replace my email address with a rethinkdb one

* update bugs email address

Author: gabor-boros

package.json

@@ -7,7 +7,7 @@
     "homepage": "https://rethinkdb.com",
     "bugs": {
         "url": "https://github.com/rethinkdb/rethinkdb/issues",
-        "email": "gabor.brs@gmail.com"
+        "email": "bugs@rethinkdb.com"
     },
     "files": ["rethinkdb.js", "ast.js", "net.js", "util.js", "errors.js", "cursor.js", "README.md", "proto-def.js"],
     "repository": {