remove Swift 5's experimental feature

Author: sebsto

Package.swift

@@ -20,8 +20,7 @@ let package = Package(
                 .product(name: "AWSLambdaEvents", package: "swift-aws-lambda-events"),
                 .product(name: "OpenAPIRuntime", package: "swift-openapi-runtime"),
             ],
-            path: "Sources",
-            swiftSettings: [.enableExperimentalFeature("StrictConcurrency=complete")]
+            path: "Sources"
         ),
         // test targets
         .testTarget(