Fix system metrics unit tests on mac (#3638)

* Fix system metrics unit tests on mac

Don't test for system.network.connections on mac

* round

Author: david-gang

instrumentation/opentelemetry-instrumentation-system-metrics/tests/test_system_metrics.py

@@ -113,7 +113,6 @@ def test_system_metrics_instrument(self):
             "system.network.packets",
             "system.network.errors",
             "system.network.io",
-            "system.network.connections",
             "system.thread_count",
             "process.context_switches",
             "process.cpu.time",
@@ -137,6 +136,8 @@ def test_system_metrics_instrument(self):
             observer_names.append(
                 f"process.runtime.{self.implementation}.gc_count",
             )
+        if sys.platform != "darwin":
+            observer_names.append("system.network.connections")
 
         self.assertEqual(sorted(metric_names), sorted(observer_names))
 
@@ -767,6 +768,7 @@ def test_system_network_io(self, mock_net_io_counters):
         ]
         self._test_metrics("system.network.io", expected)
 
+    @skipIf(sys.platform == "darwin", "No network connections on macOS")
     @mock.patch("psutil.net_connections")
     def test_system_network_connections(self, mock_net_connections):
         NetConnection = namedtuple(