Fix API examples

We were getting many errors when trying to run them, from uninitialized
constant `HTTP` to undefined method `headers`.

We might move these examples to the documentation repository in the
future, but we need to look for possible side-effects first.

doc/api/examples/ruby/example_1.rb

@@ -1,13 +1,16 @@
-require "http"
+require "net/http"
 
 API_ENDPOINT = "https://demo.consulproject.org/graphql".freeze
 
 def make_request(query_string)
-  HTTP.headers("User-Agent" => "Mozilla/5.0", accept: "application/json")
-      .get(
-        API_ENDPOINT,
-        params: { query: query_string.delete("\n").delete(" ") }
-      )
+  uri = URI(API_ENDPOINT)
+  uri.query = URI.encode_www_form(query: query_string.delete("\n").delete(" "))
+  request = Net::HTTP::Get.new(uri)
+  request[:accept] = "application/json"
+
+  Net::HTTP.start(uri.hostname, uri.port, use_ssl: true) do |https|
+    https.request(request)
+  end
 end
 
 query = <<-GRAPHQL