Fix index.d.ts for *reactour* by correcting typo (#37438)

* Fixed the declaration file for the 'showButtons' prop, as it was previously 'showButton' and it couldn't be used effectively with Typescript

* fix-reactour-showButtons update test

types/reactour/index.d.ts

@@ -197,7 +197,7 @@ export interface ReactourProps {
      * Show/Hide _Helper_ Navigation buttons
      * @default true
      */
-    showButton?: boolean;
+    showButtons?: boolean;
 
     /**
      * Show/Hide _Helper_ Close button

types/reactour/reactour-tests.tsx

@@ -131,7 +131,7 @@ class CustomTour extends React.Component<{}, { isTourOpen: boolean }> {
                     scrollDuration={100}
                     scrollOffset={1}
                     showNumber={false}
-                    showButton={false}
+                    showButtons={false}
                     showCloseButton={false}
                     showNavigation={false}
                     showNavigationNumber={false}