Remove "Hotspot" key from settings search if not needed

- Remove "Hotspot" search key from TetherSettings

- Disable page search from WifiTetherSettings

Bug: 243876722
Test: manual test
make RunSettingsRoboTests ROBOTEST_FILTER=TetherSettingsTest
make RunSettingsRoboTests ROBOTEST_FILTER=WifiTetherSettingsTest

Change-Id: Ie04027600663321b35d8309c59084f630103e959