Removes the dashboard with alerts file

Alerts are not managed by the dashboard so the file can
simply be removed in favor of the functionality in the panels.

app/assets/javascripts/monitoring/components/dashboard_with_alerts.vue

-<script>
-import CeDashboard from '~/monitoring/components/dashboard.vue';
-import AlertWidget from './alert_widget.vue';
-
-export default {
-  components: {
-    AlertWidget,
-  },
-  extends: CeDashboard,
-  data() {
-    return {
-      allAlerts: {},
-    };
-  },
-  methods: {
-    setAlerts(alertPath, alertAttributes) {
-      if (alertAttributes) {
-        this.$set(this.allAlerts, alertPath, alertAttributes);
-      } else {
-        this.$delete(this.allAlerts, alertPath);
-      }
-    },
-  },
-};
-</script>

app/assets/javascripts/monitoring/monitoring_bundle.js

 import Vue from 'vue';
 import { GlToast } from '@gitlab/ui';
-import Dashboard from '~/monitoring/components/dashboard_with_alerts.vue';
+import Dashboard from '~/monitoring/components/dashboard.vue';
 import { parseBoolean } from '~/lib/utils/common_utils';
 import { getParameterValues } from '~/lib/utils/url_utility';
 import store from './stores';

spec/frontend/monitoring/components/dashboard_spec.js

@@ -6,7 +6,7 @@ import MockAdapter from 'axios-mock-adapter';
 import axios from '~/lib/utils/axios_utils';
 import statusCodes from '~/lib/utils/http_status';
 import { metricStates } from '~/monitoring/constants';
-import Dashboard from '~/monitoring/components/dashboard_with_alerts.vue';
+import Dashboard from '~/monitoring/components/dashboard.vue';
 
 import DateTimePicker from '~/vue_shared/components/date_time_picker/date_time_picker.vue';
 import CustomMetricsFormFields from '~/custom_metrics/components/custom_metrics_form_fields.vue';