docs - grouped horizontal bar

```
x = [1980 1990 2000];
y = [8 15 25; 30 35 40; 50 55 62];

% Grouped
tiledlayout(2,1);
ax1 = nexttile;
barh(ax1,x,y)
title('Grouped Style')

% Stacked
ax2 = nexttile;
barh(ax2,x,y,'stacked')
title('Stacked Style')

fig2plotly(gcf);
```

Plot on the top subplot is not generated properly.