chore: remove offset option

Author: leodemoura

src/Init/Grind/Config.lean

@@ -153,11 +153,6 @@ structure Config where
   at least `Std.IsPreorder`
   -/
   order := true
-  /--
-  When `true` (default: `true`), enables the legacy module `offset`. This module will be deleted in
-  the future.
-  -/
-  offset := true
   deriving Inhabited, BEq
 
 /--