remove dwsmart's mastadon link (#4213)

Author: dwsmart

src/config/contributors.json

@@ -1243,7 +1243,6 @@
     "bluesky": "tamethebots.com",
     "github": "dwsmart",
     "linkedin": "davewsmart",
-    "mastodon": "https://seocommunity.social/@dwsmart",
     "name": "Dave Smart",
     "teams": {
       "2020": [