Simplify build by using the standard Amazon Linux 2 / Swift docker images

[sebsto]

The change to include openssl-devel landed in the Amazon Linux 2 Swift container image build by Apple thanks to swiftlang/swift-docker#371.

It's now time to update the Makefile in each template to simplify and remove the need to build a custom container.

I think just two changes are required (in each template)

1. change the value of DOCKER_IMAGE to swift:5.10-amazonlinux2
   

   aws-lambda-swift-sam-template/templates/api-to-lambda/{{cookiecutter.__project_name}}/Makefile

   Line 18 in d311397

   DOCKER_IMAGE := swift-lambda-builder-workaround

   I assume we only support the latest version of Swift, no more.

2. Delete this line
   

   aws-lambda-swift-sam-template/templates/api-to-lambda/{{cookiecutter.__project_name}}/Makefile

   Line 25 in d311397

   docker inspect $(DOCKER_IMAGE) >/dev/null 2>&1 || docker build -t $(DOCKER_IMAGE) .; \