Remove Twitter icon

Not a fan of X/Grok/Musk. Haven't used my account in a long time, but
I'm keeping it just so nobody takes the name.

Author: dgmstuart

_config.yml

@@ -9,7 +9,6 @@ url: "https://dgmstuart.github.io"
 date_format: "%-d %b, %Y"
 animated: false
 
-twitter_username: dgmstuart
 github_username:  dgmstuart
 disqus_shortname: dgmscode
 stackoverflow_id: 1035431/dgmstuart