bug: AXE: Elements must use only allowed ARIA attributes for ion-select

# Bug Report

**Ionic version:**

[ ] **4.x**
[x] **5.x**

**Current behavior:**
Axe issue - Elements must use only allowed ARIA attributes for ionselect.

Running AXE on the app linked below I get the following for ion-select:

```
Fix the following:
ARIA attribute is not allowed: aria-required="true"
```

**Expected behavior:**
Would be able to use aria-required on an ion-select without the AXE error.

**Related code:**

https://github.com/ionic-afl/ionic-v5-observations.git

Start by reproducing the AXE violation in the linked ionic-v5-observations app with ion-select and aria-required="true". Trace the ion-select ARIA handling in the Ionic framework and verify the fix by rerunning AXE, with completion marked by no disallowed-attribute violation.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.