Fix file name and add license header

Author: DougGregor

Tests/SwiftOperatorsTest/OperatorTable.swift renamed to Tests/SwiftOperatorsTest/OperatorTableTests.swift

@@ -1,3 +1,14 @@
+//===------------------ OperatorTableTests.swift --------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2022 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
 import XCTest
 import SwiftSyntax
 import SwiftParser