[5.5] Clear user instance on rebind request

[abler98]

Because it could change the credentials

[stremovskyy]

+1

[sisve]

Would this deserve a test to ensure it stays this way?

[timoschwarzer]

This commit breaks all my unit tests that use the actingAs helper.
I use Laravel Passport and a simple test like this fails.

// $this->user is a User instance
$this->actingAs($this->user, 'api');
$this
    ->get('/api/v2/user')
    ->assertStatus(200);

The test passes when I revert this commit.

[devcircus]

This wrecks my tests.

[Thijmen]

Wrecks my tests also @taylorotwell

[riseno]

same here, all tests failed @taylorotwell

[Thijmen]

Luckely there is a new PR to revert this: #22815