Update unit to seconds in GraphQL logs

We changed the unit name but the duration conversion is happening
from seconds to nanoseconds instead of leaving as seconds as the field
is now called.

lib/gitlab/graphql/query_analyzers/logger_analyzer.rb

@@ -52,8 +52,7 @@ module Gitlab
         end
 
         def duration(time_started)
-          nanoseconds = Gitlab::Metrics::System.monotonic_time - time_started
-          nanoseconds * 1000000
+          Gitlab::Metrics::System.monotonic_time - time_started
         end
 
         def default_initial_values(query)

spec/lib/gitlab/graphql/query_analyzers/logger_analyzer_spec.rb

@@ -17,9 +17,27 @@ RSpec.describe Gitlab::Graphql::QueryAnalyzers::LoggerAnalyzer do
     end
 
     context 'feature flag enabled by default' do
+      let(:monotonic_time_before) { 42 }
+      let(:monotonic_time_after) { 500 }
+      let(:monotonic_time_duration) { monotonic_time_after - monotonic_time_before }
+
       it 'enables the analyzer' do
         expect(subject.analyze?(anything)).to be_truthy
       end
+
+      it 'returns a duration in seconds' do
+        allow(GraphQL::Analysis).to receive(:analyze_query).and_return([4, 2])
+        allow(Gitlab::Metrics::System).to receive(:monotonic_time).and_return(monotonic_time_before, monotonic_time_after)
+        allow(Gitlab::GraphqlLogger).to receive(:info)
+
+        expected_duration = monotonic_time_duration
+        memo = subject.initial_value(spy('query'))
+
+        subject.final_value(memo)
+
+        expect(memo).to have_key(:duration_s)
+        expect(memo[:duration_s]).to eq(expected_duration)
+      end
     end
   end
 end