refactor(item): remove deprecated apis (#29102)

BREAKING CHANGE:

- The `helper` slot has been removed. Developers should use the `helperText` property on `ion-input` and `ion-textarea`.
- The `error` slot has been removed. Developers should use the `errorText` property on `ion-input` and `ion-textarea`.
- Counter functionality has been removed including the `counter` and `counterFormatter` properties. Developers should use the properties of the same name on `ion-input` and `ion-textarea`.
- The `fill` property has been removed. Developers should use the property of the same name on `ion-input`, `ion-select`, and `ion-textarea`.
- The `shape` property has been removed. Developers should use the property of the same name on `ion-input`, `ion-select`, and `ion-textarea`.

packages/vue/src/proxies.ts

@@ -443,17 +443,13 @@ export const IonItem = /*@__PURE__*/ defineContainer<JSX.IonItem>('ion-item', de
   'detailIcon',
   'disabled',
   'download',
-  'fill',
-  'shape',
   'href',
   'rel',
   'lines',
-  'counter',
   'routerAnimation',
   'routerDirection',
   'target',
-  'type',
-  'counterFormatter'
+  'type'
 ]);