remove built-in reader and printing support for Honu

This is a backward-incompatible change, but I think it's
unlikely that any code depends on the removed bindings
or reader syntax.

original commit: ec380e34ede09586966de5e18e7e7a32a1838d8e

collects/macro-debugger/syntax-browser/pretty-helper.rkt

@@ -28,8 +28,7 @@
      [print-struct #t]
      [print-box #t]
      [print-vector-length #f]
-     [print-hash-table #t]
-     [print-honu #f])
+     [print-hash-table #t])
     (pretty-write datum port)))
 
 (define-struct syntax-dummy (val))