bug(MatTable): Sorting arrow in header does not update on sortChange from outside

[akottr]

Reproduction

Use StackBlitz to reproduce your issue: https://stackblitz.com/edit/angular-fhtjni

Steps to reproduce:

1. Click on 'sort by name'
2. Table is sorted but arrow up (asc search) does not show up

Expected Behavior

What behavior were you expecting to see?
Arrow in the header should follow the sorting order

Actual Behavior

What behavior did you actually see?
No sorting arrow in the header is shown

Environment

• Angular: 10.1.0
• CDK/Material: 10.2.0
• Browser(s): chrome
• Operating System (e.g. Windows, macOS, Ubuntu): ubuntu

[crisbeto]

I believe this is the same underlying issue as #19467.

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