passpoint: remove @throws UnsupportedOperationException

Update the javadoc for Passpoint APIs to remove @throws
UnsupportedOperation Exception when the Passpoint is not enabled on the
device.

Bug: 121078741
Test: ./frameworks/base/wifi/tests/runtests.sh
Change-Id: I087a595c04b926a76b6ea9d6f2a475e12033815b
Signed-off-by: Ecco Park <eccopark@google.com>