Fix kwargs deprecation warnings in config entry specs

This commit fixes the warning:

Passing the keyword argument as the last hash parameter is deprecated.

spec/lib/gitlab/ci/config/entry/processable_spec.rb

@@ -361,7 +361,7 @@ RSpec.describe Gitlab::Ci::Config::Entry::Processable do
         context 'when root yaml variables are used' do
           let(:variables) do
             Gitlab::Ci::Config::Entry::Variables.new(
-              A: 'root', C: 'root', D: 'root'
+              { A: 'root', C: 'root', D: 'root' }
             ).value
           end
 

spec/lib/gitlab/config/entry/configurable_spec.rb

@@ -15,7 +15,7 @@ RSpec.describe Gitlab::Config::Entry::Configurable do
 
   describe 'validations' do
     context 'when entry is a hash' do
-      let(:instance) { entry.new(key: 'value') }
+      let(:instance) { entry.new({ key: 'value' }) }
 
       it 'correctly validates an instance' do
         expect(instance).to be_valid