remove QT4 references

src/Mod/TechDraw/Gui/TaskRichAnno.cpp

@@ -228,7 +228,6 @@ void TaskRichAnno::setUiPrimary()
     MRichTextEdit mre;
     ui->teAnnoText->setFontPointSize(mre.getDefFontSizeNum());
     // set a placeholder text to inform the user
-    // (QTextEdit has no placeholderText property in Qt4)
     ui->teAnnoText->setPlaceholderText(tr("Input the annotation text directly or start the rich text editor"));
 }