snap: remove usage from snap description

snap/snapcraft.yaml

@@ -8,21 +8,6 @@ description: |
   filesystem which can be packaged into an OCI-compliant
   container image or similar.
 
-  Usage: chisel <command> [<options>...]
-
-  Commands can be classified as follows:
-
-    Basic (general operations):
-      find     Find existing slices
-      info     Show information about package slices
-      help     Show help about a command
-      version  Show version details
-
-    Action (make things happen):
-      cut      Cut a tree with selected slices
-
-  For more information about a command, run 'chisel help <command>'.
-
   This snap can only install the slices in a location inside the
   user $HOME directory i.e. the --root option in "cut" command
   should have a location inside the user $HOME directory.