[mediasession] Re-enable tests.

Underlying flakyness issue resolved in I7e3fcf1aa278d61f721d1ebf0c3fe8783fd7f3c9

MTWN-220 #done

TEST: fx run-test mediasession_tests, 1000 times
Change-Id: Iabe2c1fa9736718dbb6aae023e393ab93b0681f1
diff --git a/bin/mediasession/src/test.rs b/bin/mediasession/src/test.rs
index da75afc..88d8d57 100644
--- a/bin/mediasession/src/test.rs
+++ b/bin/mediasession/src/test.rs
@@ -2,5 +2,4 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// TODO(turnage): Re-enable; MTWN-220
-// mod integration;
+mod integration;