chore: Remove unused namespace

Author: jeromelaban

test/OpenTelemetry.Tests/Metrics/MetricPointReclaimTests.cs

@@ -2,7 +2,6 @@
 // SPDX-License-Identifier: Apache-2.0
 
 using System.Diagnostics.Metrics;
-using Microsoft.ApplicationInsights.Extensibility.Implementation;
 using OpenTelemetry.Tests;
 using Xunit;