updating default positioning (#2827)

Author: LFDanLu

packages/@react-spectrum/contextualhelp/src/ContextualHelp.tsx

@@ -25,7 +25,7 @@ import {useMessageFormatter} from '@react-aria/i18n';
 function ContextualHelp(props: SpectrumContextualHelpProps) {
   let {
     variant = 'help',
-    placement = 'bottom end',
+    placement = 'bottom start',
     children,
     ...otherProps} = props;