Fix 'potential memory leak' compiler warning.

This CL fixes the following compiler warning:

frameworks/av/media/libstagefright/SampleTable.cpp:569:9: warning:
 Memory allocated by 'new[]' should be deallocated by 'delete[]', not
 'delete'.

Bug: 33137046
Test: Compiled with change; no warning generated.

Change-Id: I29abd90e02bf482fa840d1f7206ebbdacf7dfa37