ENF: Fix average RSSI calculation

Correctly discard new measurements when the reported timestamp is older
than the timestamp in the database.
Fixes microg#1655.

play-services-nearby-core/src/main/kotlin/org/microg/gms/nearby/exposurenotification/ExposureDatabase.kt

@@ -181,7 +181,7 @@ class ExposureDatabase private constructor(private val context: Context) : SQLit
     }
 
     fun noteAdvertisement(rpi: ByteArray, aem: ByteArray, rssi: Int, timestamp: Long = Date().time) = writableDatabase.run {
-        val update = compileStatement("UPDATE $TABLE_ADVERTISEMENTS SET rssi = IFNULL(((rssi * duration) + (? * MIN(0, ? - timestamp - duration))) / MAX(duration, ? - timestamp), -100), duration = MAX(duration, ? - timestamp) WHERE rpi = ? AND timestamp > ? AND timestamp < ?").run {
+        val update = compileStatement("UPDATE $TABLE_ADVERTISEMENTS SET rssi = IFNULL(((rssi * duration) + (? * MAX(0, ? - timestamp - duration))) / MAX(duration, ? - timestamp), -100), duration = MAX(duration, ? - timestamp) WHERE rpi = ? AND timestamp > ? AND timestamp < ?").run {
             bindLong(1, rssi.toLong())
             bindLong(2, timestamp)
             bindLong(3, timestamp)