Deal with rackup 2.2 release.

Rackup 2.2 no longer depends on `webrick`, and our usage of `rackup` fails
if we don't add a dependency on `webrick`. For details on the `rackup`
change, see:

rack/rackup#23

Note that the `rackup` maintainers recommend using `falcon` or `puma`
instead of `webrick`. However, `falcon` and `puma` are heavier weight.
`falcon` has lots of runtime dependencies and `puma` depends on `nio4r`
which has native code. As a result, it's more likely to hit installation
issues for ElasticGraph users than `webrick`. So for now we are sticking
with `webrick` but I'm open to changing this in the future.

elasticgraph-apollo/apollo_tests_implementation/Gemfile

@@ -24,4 +24,5 @@ source "https://rubygems.org"
   gem "elasticgraph-#{suffix}", path: "elasticgraph-#{suffix}"
 end
 
-gem "rackup", "~> 2.1"
+gem "rackup", "~> 2.2"
+gem "webrick", "~> 1.9"

elasticgraph-local/elasticgraph-local.gemspec

@@ -16,8 +16,9 @@ ElasticGraphGemspecHelper.define_elasticgraph_gem(gemspec_file: __FILE__, catego
   spec.add_dependency "elasticgraph-indexer", eg_version
   spec.add_dependency "elasticgraph-rack", eg_version
   spec.add_dependency "elasticgraph-schema_definition", eg_version
-  spec.add_dependency "rackup", "~> 2.1"
+  spec.add_dependency "rackup", "~> 2.2"
   spec.add_dependency "rake", "~> 13.2"
+  spec.add_dependency "webrick", "~> 1.9"
 
   spec.add_development_dependency "elasticgraph-elasticsearch", eg_version
   spec.add_development_dependency "elasticgraph-opensearch", eg_version