Fix typo for area chart embeds

app/presenters/projects/prometheus/alert_presenter.rb

@@ -183,7 +183,7 @@ module Projects
         {
           panel_groups: [{
             panels: [{
-              type: 'line-graph',
+              type: 'area-chart',
               title: title,
               y_label: y_label,
               metrics: [{

spec/features/markdown/metrics_spec.rb

@@ -142,11 +142,11 @@ RSpec.describe 'Metrics rendering', :js, :kubeclient, :use_clean_rails_memory_st
       {
         panel_groups: [{
           panels: [{
-            type: "line-graph",
+            type: 'area-chart',
             title: title,
-            y_label: "metric",
+            y_label: 'metric',
             metrics: [{
-              query_range: "metric * 0.5 < 1"
+              query_range: 'metric * 0.5 < 1'
             }]
           }]
         }]

spec/support/shared_contexts/prometheus/alert_shared_context.rb

@@ -15,7 +15,7 @@ RSpec.shared_context 'self-managed prometheus alert attributes' do
     {
       panel_groups: [{
         panels: [{
-          type: 'line-graph',
+          type: 'area-chart',
           title: title,
           y_label: y_label,
           metrics: [{ query_range: query }]