Remove exception check in testWipeData CTS test

After ag/567397, DevicePolicyManagerService.WipeData()
will no longer raise a security exception when called
with ERASE_EXTERNAL_STORAGE flag from a managed profile.
As a result, we should no longer test for that exception
path either.

Bug: 18925478
Change-Id: I6982144956508d1bbed23cd2fd20383cce0838cb
1 file changed