shell/exercises/hearing: Replace 2012-04-uchichicago commit with 2012-02-trieste

Replace the copy-paste bf93a25 (added data, 2012-03-20) from the
Chicago boot camp with the earlier 3e24204 (Added Da for Shell
example, 2012-01-30) from the Trieste boot camp [2].

[1]: https://github.com/thehackerwithin/UofCSCBC2012
[2]: https://github.com/thehackerwithin/PyTrieste

diff --git a/shell b/shell
index 0280d05f8b0b7d67cf07f7946d89e93e66e4b50a..ae8c89439ea0c6d78832e2a77858412318237a02 160000 (submodule)
--- a/shell
+++ b/shell
@@ -1 +1 @@
-Subproject commit 0280d05f8b0b7d67cf07f7946d89e93e66e4b50a
+Subproject commit ae8c89439ea0c6d78832e2a77858412318237a02