Revert "relearn: bump version to v7.0.0" NOT WORKING

archetypes stopped working, probably other things need work too.
rolling back to v6.4.1 as last working version.

probably won't update anymore since there are plans to migrate to
docsify or liascript.

This reverts commit 53b3e57.

docker/install-relearn.sh

@@ -1,7 +1,7 @@
 #!/bin/sh
 
 ## Versions
-export RELEARN="7.0.0"
+export RELEARN="6.4.1"
 # set XDG_DATA_HOME externally
 
 ## Hugo Relearn Theme: https://github.com/McShelby/hugo-theme-relearn/releases/latest/