Fix compile time warnings for unused variables

It fixes:
  warning: assigned but unused variable - VAR

ee/lib/status_page/storage/s3_client.rb

@@ -57,7 +57,7 @@ module StatusPage
       # Return a Set of all keys with a given prefix
       def list_object_keys(prefix)
         wrap_errors(prefix: prefix) do
-          list_objects(prefix).reduce(Set.new) do |objects, (response, index)|
+          list_objects(prefix).reduce(Set.new) do |objects, (response, _index)|
             break objects if objects.size >= StatusPage::Storage::MAX_UPLOADS
 
             objects | response.contents.map(&:key)

lib/gitlab/ci/reports/test_reports.rb

@@ -43,9 +43,7 @@ module Gitlab
         end
 
         def suite_errors
-          test_suites.each_with_object({}) do |(name, suite), errors|
-            errors[suite.name] = suite.suite_error if suite.suite_error
-          end
+          test_suites.transform_values(&:suite_error).compact
         end
 
         TestCase::STATUS_TYPES.each do |status_type|

spec/lib/gitlab/job_waiter_spec.rb

@@ -60,16 +60,14 @@ RSpec.describe Gitlab::JobWaiter do
         described_class.notify(waiter.key, 'a')
         described_class.notify(waiter.key, 'b')
 
-        result = nil
-        expect { Timeout.timeout(1) { result = waiter.wait(2) } }.not_to raise_error
+        expect { Timeout.timeout(1) { waiter.wait(2) } }.not_to raise_error
       end
 
       it 'increments job_waiter_started_total and job_waiter_timeouts_total when it times out' do
         expect(started_total).to receive(:increment).with(worker: 'Foo')
         expect(timeouts_total).to receive(:increment).with(worker: 'Foo')
 
-        result = nil
-        expect { Timeout.timeout(2) { result = waiter.wait(1) } }.not_to raise_error
+        expect { Timeout.timeout(2) { waiter.wait(1) } }.not_to raise_error
       end
     end
   end