Book form: can now click "start read" even when the book is marked as read

It will do the same behavior as clicking on the "read" button again to
cancel it.

front/src/BookFormIcons.vue

@@ -61,8 +61,7 @@ async function onStartReadIconClick() {
         icon="BIconBook"
         :legend="$t('bookform.wantread')"
         :is-set="isStartReadExpanded()"
-        :is-readonly="props.read"
-        @click="props.read ? null : onStartReadIconClick()"
+        @click="onStartReadIconClick"
       />
     </div>
     <div
@@ -82,7 +81,6 @@ async function onStartReadIconClick() {
       :legend="$t('bookform.startread')"
       :start-read-date="props.startReadDate"
       :is-expanded="isStartReadExpanded()"
-      :is-readonly="props.read"
       @onStartDateChange="(d) => $emit('onStartReadDateChange', d)"
       @onIconClick="onStartReadIconClick"
     />