refactor(core): mark FileManager and DataContext as sealed

Both of the classes are not meant to be overriden, so make it explicit by marking them as sealed.

Filer.EntityFrameworkCore/DataContext.cs

@@ -7,7 +7,7 @@ namespace Filer.EntityFrameworkCore
 	/// <summary>
 	/// Represents a single unit of work.
 	/// </summary>
-	public class DataContext : IDisposable
+	public sealed class DataContext : IDisposable
 	{
 		/// <summary>
 		/// Instantiates a new instance of the DataContext class.
@@ -28,8 +28,6 @@ public void Dispose()
 				this.DbContext.Dispose();
 				this.DbContext = null;
 			}
-
-			GC.SuppressFinalize(this);
 		}
 
 		/// <summary>

Filer.EntityFrameworkCore/FileManager.cs

@@ -1,4 +1,4 @@
-namespace Filer.EntityFrameworkCore
+namespace Filer.EntityFrameworkCore
 {
 	using System;
 	using System.Collections.Generic;
@@ -14,7 +14,7 @@
 	/// <summary>
 	/// Manages files in the FileStore repository.
 	/// </summary>
-	public class FileManager : IFileManager
+	public sealed class FileManager : IFileManager
 	{
 		private readonly FileStoreContext dbContext;
 
@@ -241,7 +241,6 @@ public async Task DetachFileFromContextsAsync(int fileId, params string[] contex
 		public void Dispose()
 		{
 			this.dbContext?.Dispose();
-			GC.SuppressFinalize(this);
 		}
 
 		/// <inheritdoc />