Remove unused field

src/EditorFeatures/CSharp/FindUsages/CSharpFindUsagesLSPService.cs

@@ -15,8 +15,7 @@ internal class CSharpFindUsagesLSPService : AbstractFindUsagesService
     {
         [ImportingConstructor]
         [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
-        public CSharpFindUsagesLSPService(IThreadingContext threadingContext)
-            : base(threadingContext)
+        public CSharpFindUsagesLSPService()
         {
         }
     }

src/EditorFeatures/CSharp/FindUsages/CSharpFindUsagesService.cs

@@ -17,8 +17,7 @@ internal class CSharpFindUsagesService : AbstractFindUsagesService
     {
         [ImportingConstructor]
         [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
-        public CSharpFindUsagesService(IThreadingContext threadingContext)
-            : base(threadingContext)
+        public CSharpFindUsagesService()
         {
         }
     }

src/EditorFeatures/Core/FindUsages/AbstractFindUsagesService.cs

@@ -10,9 +10,5 @@ namespace Microsoft.CodeAnalysis.Editor.FindUsages
 {
     internal abstract partial class AbstractFindUsagesService : IFindUsagesService, IFindUsagesLSPService
     {
-        private readonly IThreadingContext _threadingContext;
-
-        protected AbstractFindUsagesService(IThreadingContext threadingContext)
-            => _threadingContext = threadingContext;
     }
 }

src/EditorFeatures/VisualBasic/FindUsages/VisualBasicFindUsagesLSPService.vb

@@ -14,8 +14,7 @@ Namespace Microsoft.CodeAnalysis.Editor.VisualBasic.FindUsages
 
         <ImportingConstructor>
         <Obsolete(MefConstruction.ImportingConstructorMessage, True)>
-        Public Sub New(threadingContext As IThreadingContext)
-            MyBase.New(threadingContext)
+        Public Sub New()
         End Sub
     End Class
 End Namespace

src/EditorFeatures/VisualBasic/FindUsages/VisualBasicFindUsagesService.vb

@@ -14,8 +14,7 @@ Namespace Microsoft.CodeAnalysis.Editor.VisualBasic.FindUsages
 
         <ImportingConstructor>
         <Obsolete(MefConstruction.ImportingConstructorMessage, True)>
-        Public Sub New(threadingContext As IThreadingContext)
-            MyBase.New(threadingContext)
+        Public Sub New()
         End Sub
     End Class
 End Namespace