Could not create AST on opening AST view

```java
package nn;

public class ZZ {
public void foo(Integer n) {
switch (n) {
case Integer x when x.equals(10) -> {
}
case Comparable y -> {
}
}
;
}
}
```

- Open a Java file with the above code.
- Open AST view.
- The following exception was thrown:

```
org.eclipse.core.runtime.CoreException: Could not create AST:
Operation only supported in JLS21 AST
at org.eclipse.jdt.astview.views.ASTView.internalSetInput(ASTView.java:562)
at org.eclipse.jdt.astview.views.ASTView.refreshAST(ASTView.java:1132)
at org.eclipse.jdt.astview.views.ASTView.setASTLevel(ASTView.java:1143)
at org.eclipse.jdt.astview.views.ASTView$ASTLevelToggle.run(ASTView.java:186)
at org.eclipse.jface.action.Action.runWithEvent(Action.java:474)
at org.eclipse.jface.action.ActionContributionItem.handleWidgetSelection(ActionContributionItem.java:581)
at org.eclipse.jface.action.ActionContributionItem.lambda$4(ActionContributionItem.java:415)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:91)
at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4660)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1657)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1680)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1665)
at org.eclipse.swt.widgets.Widget.notifyListeners(Widget.java:1394)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4427)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:4003)
at org.eclipse.e4.ui.workbench.renderers.swt.StackRenderer.showMenu(StackRenderer.java:1436)
at org.eclipse.e4.ui.workbench.renderers.swt.StackRenderer$1.widgetSelected(StackRenderer.java:859)
at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:286)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:91)
at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4660)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1657)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1680)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1665)
at org.eclipse.swt.widgets.Widget.notifyListeners(Widget.java:1394)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4427)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:4003)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$5.run(PartRenderingEngine.java:1151)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:339)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1042)
at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:153)
at org.eclipse.ui.internal.Workbench.lambda$3(Workbench.java:665)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:339)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:573)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:173)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:178)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:208)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:143)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:109)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:439)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:271)
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
at java.base/java.lang.reflect.Method.invoke(Method.java:580)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:668)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:605)
at org.eclipse.equinox.launcher.Main.run(Main.java:1481)
at org.eclipse.equinox.launcher.Main.main(Main.java:1454)
```

Reproduce the failure by opening the supplied Java code in the AST view, then inspect org.eclipse.jdt.astview.views.ASTView.java around line 562 and the AST level handling shown in the stack trace. Done means the AST view opens this code without throwing the JLS21 CoreException.

Written by the indexing model from the issue text.