Remove deprecated recommendation request code.

Removed all deprecated code related to network recommendation
requests.

Test: adb shell am instrument -e class android.net.NetworkRecommendationProviderTest -w com.android.frameworks.coretests/android.support.test.runner.AndroidJUnitRunner
Test: runtest frameworks-services -c com.android.server.NetworkScorerAppManagerTest
Test: runtest frameworks-services -c com.android.server.NetworkScoreServiceTest
Test: gts-tradefed run gts -m GtsGmscoreHostTestCases -t com.google.android.gts.netrec.NetRecHostTest
Bug: 37357264
Change-Id: I81bb6ff6236b249b8e14058c1bfdb938451a75b0