Settings: Improve AOSP JA translations

They translated "hotspot" as "アクセスポイント"(access point) but it just gets us confused.
"テザリング"(Tethering) is preferred than "アクセスポイント"(access point) in Japanese translation.
FYI, most vendors fixed these strings e.g. Samsung and Sony.

Change-Id: If9aeaddc1750d1f8432fa4e1cb2e2ffb41f74b0a