doc: correct random.h docs after #17270

src/random.cpp

@@ -182,7 +182,7 @@ static uint64_t GetRdSeed() noexcept
 /* Access to other hardware random number generators could be added here later,
  * assuming it is sufficiently fast (in the order of a few hundred CPU cycles).
  * Slower sources should probably be invoked separately, and/or only from
- * RandAddSeedSleep (which is called during idle background operation).
+ * RandAddPeriodic (which is called once a minute).
  */
 static void InitHardwareRand() {}
 static void ReportHardwareRand() {}