Remove tests for old Swift versions

.github/workflows/build.yaml

@@ -13,7 +13,7 @@ jobs:
           'tvOS Simulator,name=Apple TV', 
           'watchOS Simulator,name=Apple Watch Series 5 - 40mm'
         ]
-        swift-version: [5.0, 4.2, 4.0]
+        swift-version: [5.0]
     steps:
       - uses: actions/checkout@v1
       - uses: actions/cache@v1

fastlane/Fastfile

@@ -7,19 +7,8 @@ platform :ios do
   desc "Runs all the tests"
   lane :tests do
     test(destination: "platform=macOS", swift_version: "5.0")
-    test(destination: "platform=macOS", swift_version: "4.2")
-    test(destination: "platform=macOS", swift_version: "4.0")
-
     test(destination: "platform=iOS Simulator,name=iPhone 8", swift_version: "5.0")
-    test(destination: "platform=iOS Simulator,name=iPhone 8", swift_version: "4.2")
-    test(destination: "platform=iOS Simulator,name=iPhone 8", swift_version: "4.0")
-    
     test(destination: "platform=tvOS Simulator,name=Apple TV", swift_version: "5.0")
-    test(destination: "platform=tvOS Simulator,name=Apple TV", swift_version: "4.2")
-    test(destination: "platform=tvOS Simulator,name=Apple TV", swift_version: "4.0")
-    
-    build(destination: "platform=watchOS Simulator,name=Apple Watch Series 5 - 40mm", swift_version: "4.0")
-    build(destination: "platform=watchOS Simulator,name=Apple Watch Series 5 - 40mm", swift_version: "4.2")
     build(destination: "platform=watchOS Simulator,name=Apple Watch Series 5 - 40mm", swift_version: "5.0")
   end