Add tab to HEAD tags

I found this code https://github.com/ShNURoK42/yii2/blob/master/framework/helpers/BaseHtml.php#L265 with 4 space in the end of line, after EOL.
Why you not use there "\t", and can you add changes in my pull request?
The code after change will be care whit 1 tab, on each line.

Sorry for my bad Eng.