refactor(cropper): drop the cropped preview — the cleaned image is the only preview

The extra cropped-result panel duplicated what the crop pad already shows and
the cleaned image supersedes it. Removes the panel, its state, the pointer-
release refresh handlers and the app.js plumbing. The crop result is still
uploaded (croppa stays the source when nothing is cleaned).

tools/public/assets/cropper/index.html

@@ -80,17 +80,11 @@
       <div class="editor-grid mt-2">
         <div class="editor-media">
           <label class="cds--label">Original — crop it</label>
-          <div class="croppa-pad mt-1" v-on:mouseup="refreshCropPreview" v-on:touchend="refreshCropPreview">
+          <div class="croppa-pad mt-1">
             <croppa ref="croppa" v-model="myCroppa" :show-remove-button="false" :width="250" :height="267.44" :quality="2">
               <img slot="initial" crossOrigin="anonymous" :src="message.message.file_url" style="width: 300px">
             </croppa>
           </div>
-          <template v-if="cropPreview">
-            <label class="cds--label mt-2" style="display:block;">Cropped preview</label>
-            <div class="croppa-pad mt-1">
-              <img :src="cropPreview" alt="cropped preview">
-            </div>
-          </template>
           <template v-if="cleanedImage">
             <label class="cds--label mt-2" style="display:block;">Cleaned preview</label>
             <div class="croppa-pad mt-1">