Add upgrade note for changed migration behaviour

[ghostal]

Adds a note describing a fairly typical scenario where existing migrations would fail after upgrade, without an obvious documented cause.

[hafezdivandari]

Both examples work perfectly fine on Laravel 11 as expected:

public function testAddingAndRenamingColumns()
{
    Schema::create('tests', function (Blueprint $table) {
        $table->integer('votes');
    });

    Schema::table('tests', function (Blueprint $table) {
        $table->string('description')->after('votes'); // alter table `tests` add `description` varchar(255) not null after `votes`
        $table->renameColumn('votes', 'vote_count');   // alter table `tests` rename column `votes` to `vote_count`
    });

    $this->assertSame(['vote_count', 'description'], Schema::getColumnListing('tests'));
}

public function testRenamingAndAddingColumns()
{
    Schema::create('tests', function (Blueprint $table) {
        $table->integer('votes');
    });

    Schema::table('tests', function (Blueprint $table) {
        $table->renameColumn('votes', 'vote_count');         // alter table `tests` rename column `votes` to `vote_count`
        $table->string('description')->after('vote_count');  // alter table `tests` add `description` varchar(255) not null after `vote_count`
    });

    $this->assertSame(['vote_count', 'description'], Schema::getColumnListing('tests'));
}