fix: 修复弹窗显示时PPT iframe误加载的问题

当观察弹窗显示时，添加条件阻止PPT iframe加载，避免资源浪费和显示异常

src/components/pptEasyClass/index.vue

@@ -108,7 +108,7 @@
       <div class="pec_content">
         <iframe allow="camera *; microphone *;display-capture;midi;encrypted-media;clipboard-write;clipboard-read"
           webkitallowfullscreen="" mozallowfullscreen="" allowfullscreen="" frameborder="no" border="0" :src="iframeSrc"
-          v-if="showIframe" style="width: 100%; height: 100%; border: none" ref="ppt"></iframe>
+          v-if="showIframe && !showObserveDialog" style="width: 100%; height: 100%; border: none" ref="ppt"></iframe>
       </div>
     </div>