contrib: Remove api-coverage tool

This tool is intended for analysis on Terraform's AWS provider, but that
provider is no longer developed in this repository and so this tool is
no longer functional.

contrib/api-coverage/aws_api_coverage.rb

@@ -1,49 +0,0 @@
-#
-# This script generates CSV output reporting on the API Coverage of Terraform's
-# AWS Provider.
-#
-# In addition to Ruby, it depends on a properly configured Go development
-# environment with both terraform and aws-sdk-go present.
-#
-
-require 'csv'
-require 'json'
-require 'pathname'
-
-module APIs
-  module Terraform
-    def self.path
-      @path ||= Pathname(`go list -f '{{.Dir}}' github.com/hashicorp/terraform`.chomp)
-    end
-
-    def self.called?(api, op)
-      `git -C "#{path}" grep "#{api}.*#{op}" -- builtin/providers/aws | wc -l`.chomp.to_i > 0
-    end
-  end
-
-  module AWS
-    def self.path
-      @path ||= Pathname(`go list -f '{{.Dir}}' github.com/aws/aws-sdk-go/aws`.chomp).parent
-    end
-
-    def self.api_json_files
-      Pathname.glob(path.join('**', '*.normal.json'))
-    end
-
-    def self.each
-      api_json_files.each do |api_json_file|
-        json = JSON.parse(api_json_file.read)
-        api = api_json_file.dirname.basename
-        json["operations"].keys.each do |op|
-          yield api, op
-        end
-      end
-    end
-  end
-end
-
-csv = CSV.new($stdout)
-csv << ["API", "Operation", "Called in Terraform?"]
-APIs::AWS.each do |api, op|
-  csv << [api, op, APIs::Terraform.called?(api, op)]
-end