Update code owners to represent the team instead of someone who no lo…

…nger works on the ext

CODE_OWNERS.txt

@@ -1,15 +1,4 @@
-The following is a list of owners for different areas of the VSCode .NET Core extension code. 
-Each of the owners is responsible for ensuring that changes in their areas 
-are reviewed, either by themselves or by someone they designate, in 
-addition to being the final word for the architecture and content of an area.
+# CODEOWNERS file per https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/about-code-owners
 
-List sorted by last name and the fields are Name (N), GitHub user account (G), 
-Description (D).
-
-Note: If you don't find the area in the below list, or you have a general 
-question, send a message to Sarah Oslund (@sfoslund) or Marc Paine (@marcpopMSFT). 
-They can ensure that the question gets forwarded to theright person or answer it themselves.  
-
-N: Sarah Oslund
-G: sfoslund
-D: Everything
+# Default owners
+* @dotnet/dotnet-cli