Fix GL UI charts import paths

Some components were importing charts from GitLab UI via
`@gitlab/ui/charts` instead of the dist path `@gitlab/ui/dist/charts`.
While this didn't seem to cause any user-facing issue, we started seeing
some Jest failures after a recent update in GitLab UI to prevent
circular dependencies. Updating the import path seems to resolve the
problem.

ee/app/assets/javascripts/burndown_chart/components/burndown_chart.vue

 <script>
 import { GlButton, GlButtonGroup } from '@gitlab/ui';
-import { GlLineChart } from '@gitlab/ui/charts';
+import { GlLineChart } from '@gitlab/ui/dist/charts';
 import dateFormat from 'dateformat';
 import ResizableChartContainer from '~/vue_shared/components/resizable_chart/resizable_chart_container.vue';
 import { s__, __, sprintf } from '~/locale';

ee/app/assets/javascripts/issues_analytics/components/issues_analytics.vue

@@ -2,7 +2,7 @@
 import { mapGetters, mapActions, mapState } from 'vuex';
 import { engineeringNotation, sum, average } from '@gitlab/ui/src/utils/number_utils';
 import { GlLoadingIcon } from '@gitlab/ui';
-import { GlColumnChart, GlChartLegend } from '@gitlab/ui/charts';
+import { GlColumnChart, GlChartLegend } from '@gitlab/ui/dist/charts';
 import { s__ } from '~/locale';
 import { getMonthNames } from '~/lib/utils/datetime_utility';
 import { getSvgIconPathContent } from '~/lib/utils/icon_utils';