For #2834: Delete all Private Tabs redesign (#4787)

...c/androidTest/java/org/mozilla/fenix/ui/HomeScreenTest.kt

...roidTest/java/org/mozilla/fenix/ui/robots/BrowserRobot.kt

...dTest/java/org/mozilla/fenix/ui/robots/HomeScreenRobot.kt

...droidTest/java/org/mozilla/fenix/ui/robots/SearchRobot.kt

app/src/main/java/org/mozilla/fenix/home/HomeFragment.kt

...ix/home/sessioncontrol/viewholders/TabHeaderViewHolder.kt

app/src/main/res/layout/private_browsing_description.xml

app/src/main/res/layout/tab_header.xml

app/src/main/res/values/strings.xml