Laravel v5.7.21 released

Laravel v5.7.21 is released in 2019/01/15, here are the changes we`ve merged into this release.

#Fixed

• Fixed Blueprint::removeColumn() (#27115, #27122)
• Fixed allowing of null broadcast connection driver (#27135)
• Fixed ModelMakeCommand::handle() should always return bool value (#27156)
• Fixed TestResponse::assertSessionDoesntHaveErrors() when there is no errors (#27145)
• Fixed default message is localization twice in 403.blade.php error page (4a08120)

#Changed

• Replaced get_called_class() to static::class (#27146)
• Re-throw NoMatchingExpectationException from PendingCommand (#27158)