remove the obsolete Testing_ module, and its transitive swift-atomics dependency

Author: tayloraswift

Package.swift

@@ -6,25 +6,14 @@ let package:Package = .init(
     platforms: [.macOS(.v10_15), .iOS(.v13), .tvOS(.v13), .watchOS(.v6)],
     products: [
         .library(name: "Grammar", targets: ["Grammar"]),
-        .library(name: "Testing_", targets: ["Testing_"]),
         .library(name: "TraceableErrors", targets: ["TraceableErrors"]),
     ],
-    dependencies: [
-        //  This dependency only used for the Testing module’s concurrency support.
-        .package(url: "https://github.com/apple/swift-atomics.git", from: "1.2.0"),
-    ],
     targets: [
         .target(name: "Grammar",
             dependencies: [
                 .target(name: "TraceableErrors"),
             ]),
 
-        .target(name: "Testing_",
-            dependencies: [
-                .product(name: "Atomics", package: "swift-atomics"),
-            ],
-            path: "Sources/Testing"),
-
         .target(name: "TraceableErrors"),
     ]
 )