Updates name of the default module

conformance/system_macros/delta.ion

@@ -69,15 +69,15 @@
 // Demonstrations of some interesting things you can do with delta.
 
 (ion_1_1 "delta and repeat can be combined to generate"
-         (mactab $ion_encoding (macro from_x_count_n_by_step (x n step) (.delta (.. (%x) (.repeat (%n) (%step))))))
+         (mactab _ (macro from_x_count_n_by_step (x n step) (.delta (.. (%x) (.repeat (%n) (%step))))))
          (then "an increasing sequence"   (text "(:from_x_count_n_by_step 0 10  1)") (produces 0 1 2 3 4 5 6 7 8 9 10))
          (then "a count-by-twos sequence" (text "(:from_x_count_n_by_step 0 10  2)") (produces 0 2 4 6 8 10 12 14 16 18 20))
          (then "a decreasing sequence"    (text "(:from_x_count_n_by_step 5 10 -1)") (produces 5 4 3 2 1 0 -1 -2 -3 -4 -5)))
 
 (ion_1_1 "it is possible to create a delta of deltas encoding"
          // See, for example
          // https://www.timescale.com/blog/time-series-compression-algorithms-explained/#delta-of-delta-encoding
-         (mactab $ion_encoding
+         (mactab _
                  (macro delta_of_deltas (flex_int::init dod*) (.delta (.. (%init) (.delta (%dod)))))
                  (macro rle (flex_uint::run_length flex_int::value) (.repeat (%run_length) (%value))))
          (text "(:delta_of_deltas 52 (:: -1 (:rle 10 0) 1 (:rle 5 0) 1 (:rle 5 0)))")