Add explicit OWNERS for SystemClock and related classes

Bug: 213393821
Bug: 189810551
Change-Id: Ie0736e54f56bb749eff669ea42c25ce70ef4deb4

core/java/android/os/OWNERS

@@ -52,6 +52,9 @@ per-file *Power* = file:/services/core/java/com/android/server/power/OWNERS
 per-file *Telephony* = file:/telephony/OWNERS
 per-file *Zygote* = file:/ZYGOTE_OWNERS
 
+# Time
+per-file *Clock* = file:/services/core/java/com/android/server/timezonedetector/OWNERS
+
 # RecoverySystem
 per-file *Recovery* = file:/services/core/java/com/android/server/recoverysystem/OWNERS