remove unnecessary added tag

resource/js/components/PageEditor/CodeMirrorEditor.js

@@ -451,7 +451,6 @@ export default class CodeMirrorEditor extends AbstractEditor {
            <ReactCodeMirror
         ref="cm"
         className={this.state.additionalClass}
-        placeholder="aaaa"
         editorDidMount={(editor) => {
           // add event handlers
           editor.on('paste', this.pasteHandler);