Update _config.yml rm bluesky, mastodon icon refs

Author: reshamas

_config.yml

@@ -42,10 +42,10 @@ author:
       icon: "fab fa-fw fa-linkedin"
       url: "https://linkedin.com/company/scikit-learn/"
     - label: "Bluesky"
-      icon: "fab fa-brands fa-bluesky"
+      icon: ""
       url: "https://bsky.app/profile/scikit-learn.org"
     - label: "Mastodon"
-      icon: "fab fa-brands fa-mastodon"
+      icon: ""
       url: "https://fosstodon.org/@sklearn"
     - label: "YouTube"
       icon: "fab fa-fw fa-youtube"
@@ -69,10 +69,10 @@ footer:
       icon: "fab fa-fw fa-linkedin"
       url: "https://linkedin.com/company/scikit-learn/"
     - label: "Bluesky"
-      icon: "fab fa-brands fa-bluesky"
+      icon: ""
       url: "https://bsky.app/profile/scikit-learn.org"
     - label: "Mastodon"
-      icon: "fab fa-brands fa-mastodon"
+      icon: ""
       url: "https://fosstodon.org/@sklearn"
     - label: "YouTube"
       icon: "fab fa-fw fa-youtube"