Fix quotameter a11y label; have to work around bootstrap-vue shortcoming

here.

xref: https://dequeuniversity.com/rules/axe/4.4/aria-progressbar-name

client/src/components/Masthead/QuotaMeter.vue

@@ -5,7 +5,9 @@
                 {{ usingString + " " + totalUsageString }}
             </b-link>
             <b-link v-else v-b-tooltip.hover.left class="quota-progress" to="/storage" :title="title">
-                <b-progress :value="usage" :max="100" :variant="variant" />
+                <b-progress :max="100">
+                    <b-progress-bar aria-label="Quota usage" :value="usage" :variant="variant" />
+                </b-progress>
                 <span>{{ usingString + " " + usage.toFixed(0) }}%</span>
             </b-link>
         </div>