Remove Burton from members lists and Core Contributor status

Signed-off-by: Burton Rheutan <rheutan7@gmail.com>

Author: burtonr

_data/members.yml

@@ -5,7 +5,6 @@ founders:
 
 core:
   - lucas
-  - burton
   - stefan
 
 members:
@@ -16,6 +15,7 @@ members:
 
 # Listed for several months, GitHub and leaderboard shows former contributors permanently
 former_members:
+  - burton
   - ed
   - richard
   - john

_staff_members/burton.md

@@ -5,5 +5,5 @@ image_path: /images/author/burton.png
 twitter_username: _burtonr
 github_username: burtonr
 webpage: https://burtonr.dev/
-blurb: Core Contributor <a href="https://twitter.com/openfaas">@openfaas</a>. Software Principal Engineer <a href="https://www.delltechnologies.com">@Dell Technologies</a>
+blurb: Software Principal Engineer <a href="https://www.delltechnologies.com">@Dell Technologies</a>
 ---