update ios deployment target

Author: OhKanghoon

Package.swift

@@ -5,7 +5,7 @@ import PackageDescription
 let package = Package(
   name: "WeakMapTable",
   platforms: [
-    .macOS(.v10_11), .iOS(.v8), .tvOS(.v9), .watchOS(.v3)
+    .macOS(.v10_11), .iOS(.v9), .tvOS(.v9), .watchOS(.v3)
   ],
   products: [
     .library(name: "WeakMapTable", targets: ["WeakMapTable"]),

WeakMapTable.podspec

@@ -11,7 +11,7 @@ Pod::Spec.new do |s|
   s.frameworks   = "Foundation"
   s.swift_version = "5.1"
 
-  s.ios.deployment_target = "8.0"
+  s.ios.deployment_target = "9.0"
   s.osx.deployment_target = "10.11"
   s.tvos.deployment_target = "9.0"
   s.watchos.deployment_target = "3.0"