When phpunit.args is used, it is doubled for every repeating of the last test

[BladeMF]

Repro

1. Add some argument in config, e.g.

	"phpunit.args": [
		"--testdox"
	],

2. Run a test The command is: Executing task: /some/path/vendor/bin/phpunit' --testdox --colors=always '/some/path'
3. Execute Rerun last test The command now is: Executing task: /some/path/vendor/bin/phpunit' --testdox --colors=always --testdox --colors=always '/some/path'
4. Execute Rerun last test again. --testdox --colors=always are added again.

Expected outcome

The arguments for color and testdox to not be appended every time.

Environment	Values
Extension version	4.1.1
Operating system	Windows 10

I really enjoy using your extension! Would you mind if I PR'd this?