plugins/colorpicker: use glReadPixels instead of glReadnPixels

We always know the data for the single pixel will fit into the buffer, so
it's unnecessary to use the checked variant (which is only available in
OpenGL 4.5)

src/plugins/colorpicker/colorpicker.cpp

@@ -62,7 +62,7 @@ void ColorPickerEffect::paintScreen(const RenderTarget &renderTarget, const Rend
         constexpr GLsizei PIXEL_SIZE = 1;
         const QPoint texturePosition = viewport.mapToRenderTarget(m_scheduledPosition).toPoint();
 
-        glReadnPixels(texturePosition.x(), renderTarget.size().height() - texturePosition.y() - PIXEL_SIZE, PIXEL_SIZE, PIXEL_SIZE, GL_RGBA, GL_FLOAT, sizeof(float) * data.size(), data.data());
+        glReadPixels(texturePosition.x(), renderTarget.size().height() - texturePosition.y() - PIXEL_SIZE, PIXEL_SIZE, PIXEL_SIZE, GL_RGBA, GL_FLOAT, data.data());
         QVector3D sRGB = 255 * renderTarget.colorDescription().mapTo(QVector3D(data[0], data[1], data[2]), ColorDescription::sRGB);
         QDBusConnection::sessionBus().send(m_replyMessage.createReply(QColor(sRGB.x(), sRGB.y(), sRGB.z())));
         m_picking = false;