Address comments

Author: lihaMSFT

src/BenchmarkDotNet/Analysers/EnvironmentAnalyser.cs

@@ -1,5 +1,4 @@
 using System.Collections.Generic;
-using System.Collections.Immutable;
 using System.Linq;
 using System.Reflection;
 using System.Text;
@@ -9,7 +8,6 @@
 using BenchmarkDotNet.Reports;
 using BenchmarkDotNet.Toolchains.InProcess.Emit;
 using BenchmarkDotNet.Toolchains.InProcess.NoEmit;
-using BenchmarkDotNet.Toolchains.Results;
 
 namespace BenchmarkDotNet.Analysers
 {

src/BenchmarkDotNet/Reports/BenchmarkReport.cs

@@ -47,7 +47,7 @@ public BenchmarkReport(
                 ?? (IReadOnlyDictionary<string, Metric>)ImmutableDictionary<string, Metric>.Empty;
         }
 
-        public BenchmarkReport(BenchmarkCase benchmarkCase, GenerateResult generateResult, BuildResult buildResult)
+        internal BenchmarkReport(BenchmarkCase benchmarkCase, GenerateResult generateResult, BuildResult buildResult)
         {
             BenchmarkCase = benchmarkCase;
             GenerateResult = generateResult;