xbps/mirrors: Move Clarkson from Tier 1 to Tier 2

Clarkson reliably has sync problems and has failed to meet the quality
requirement to maintain status as a Tier 1 mirror.  As they are not
directly operated or overseen by the Void team they also don't really
satisfy the documented requirements.  As such Clarkson is now
de-listed from tier 1 status.  They remain as a Tier 2 mirror until
such time as they are not reliable enough to maintain that status.

Author: the-maldridge

src/xbps/repositories/mirrors/index.md

@@ -15,7 +15,6 @@ packages available.
 | <https://alpha.de.repo.voidlinux.org/>         | EU: Finland      |
 | <https://mirrors.servercentral.com/voidlinux/> | USA: Chicago     |
 | <https://alpha.us.repo.voidlinux.org/>         | USA: Kansas City |
-| <https://mirror.clarkson.edu/voidlinux/>       | USA: New York    |
 
 ## Tier 2 mirrors
 
@@ -49,6 +48,7 @@ sub-repository.
 | <https://ftp.acc.umu.se/mirror/voidlinux/>         | EU: Sweden        |
 | <https://ftp.lysator.liu.se/pub/voidlinux/>        | EU: Sweden        |
 | <https://ftp.sunet.se/mirror/voidlinux/>           | EU: Sweden        |
+| <https://mirror.clarkson.edu/voidlinux/>           | USA: New York     |
 
 ### Region-locked mirrors