fix: use microsecond instead of nanosecond for latency measurements (#164)

Author: supercaracal

lib/redis_client/cluster/node/latency_replica.rb

@@ -47,9 +47,9 @@ def measure_latencies(clients) # rubocop:disable Metrics/AbcSize
 
                 min = DUMMY_LATENCY_NSEC
                 MEASURE_ATTEMPT_COUNT.times do
-                  starting = Process.clock_gettime(Process::CLOCK_MONOTONIC, :nanosecond)
+                  starting = Process.clock_gettime(Process::CLOCK_MONOTONIC, :microsecond)
                   client.send(:call_once, 'PING')
-                  duration = Process.clock_gettime(Process::CLOCK_MONOTONIC, :nanosecond) - starting
+                  duration = Process.clock_gettime(Process::CLOCK_MONOTONIC, :microsecond) - starting
                   min = duration if duration < min
                 end