chore(client): tweak charts

packages/frontend/src/components/MkRetentionHeatmap.vue

@@ -10,7 +10,6 @@
 <script lang="ts" setup>
 import { markRaw, version as vueVersion, onMounted, onBeforeUnmount, nextTick } from 'vue';
 import { Chart } from 'chart.js';
-import { enUS } from 'date-fns/locale';
 import tinycolor from 'tinycolor2';
 import { MatrixController, MatrixElement } from 'chartjs-chart-matrix';
 import * as os from '@/os';