fix some warnings

'LayoutOptions.FillAndExpand' is obsolete: 'The StackLayout expansion options are deprecated; please use a Grid instead.'

Author: janusw

Source/OxyplotMauiSample/Pages/IssueDemos/Pages/AddPlotViews.xaml.cs

@@ -21,10 +21,12 @@ public void AddButtonClicked(object sender, EventArgs e)
             int n = this.layout1.Children.Count + 1;
             var pm = new PlotModel { Title = "Plot " + n, Background = backgroundColors[n % backgroundColors.Length] };
             pm.Series.Add(new FunctionSeries(x => Math.Sin(n * x), 0, 20, 500, "sin(x)"));
-            var pv = new PlotView();
-            pv.Model = pm;
-            pv.HorizontalOptions = LayoutOptions.FillAndExpand;
-            pv.HeightRequest = 200;
+            var pv = new PlotView()
+            {
+                Model = pm,
+                HorizontalOptions = LayoutOptions.Fill,
+                HeightRequest = 200,
+            };
             this.layout1.Children.Add(pv);
         }
         public void RemoveButtonClicked(object sender, EventArgs e)

Source/OxyplotMauiSample/Pages/IssueDemos/Pages/TabbedPageWithItemTemplate.cs

@@ -43,8 +43,8 @@ public SubPage()
 
                 var plotView = new PlotView
                 {
-                    HorizontalOptions = LayoutOptions.FillAndExpand,
-                    VerticalOptions = LayoutOptions.FillAndExpand,
+                    HorizontalOptions = LayoutOptions.Fill,
+                    VerticalOptions = LayoutOptions.Fill,
                     Model = plotModel
                 };