testing: bump snapshot integration tests to alpha2

Author: tylerjl

Rakefile

@@ -116,7 +116,7 @@ namespace :artifacts do
   namespace :snapshot do
     snapshots = 'https://snapshots.elastic.co/downloads/elasticsearch'
     artifacts = 'spec/fixtures/artifacts'
-    build = 'elasticsearch-6.0.0-alpha1-SNAPSHOT'
+    build = 'elasticsearch-6.0.0-alpha2-SNAPSHOT'
     %w[deb rpm].each do |ext|
       package = "#{build}.#{ext}"
       local = "#{artifacts}/#{package}"