Remove TODO in get/set parameter methods in bcradio

Methods to set and get vendor parameters in broadcast radio HAL
can be not implemented simply as key-value map since vendors could
implement flexibly based on their requirements. Therefore, it is
better not to provide implementation of set/get parameters methods
in the default HAL.

Bug: 243683842
Flag: EXEMPT bugfix
Test: atest VtsHalBroadcastradioAidlTargetTest
Change-Id: Ibec9ef7cceb95907b96e686d7af0d6d3b3b5a23e