Update .travis.yml

Author: Sumesh1294

.travis.yml

@@ -1,9 +1,9 @@
 os: osx
 language: swift
-osx_image: xcode12.2
+osx_image: xcode12.3
 xcode_project: CountriesSwiftUI.xcodeproj
 xcode_scheme: CountriesSwiftUI
 xcode_sdk: iphonesimulator14.2
 xcode_destination: platform=iOS Simulator,OS=14.2,name=iPhone 8
 after_success:
-  - bash <(curl -s https://codecov.io/bash)
+  - bash <(curl -s https://codecov.io/bash)