Fix debugbar styles printing

[paulbalandan]

Description
Fixes #5097

The truncated styles would actually not pose a problem because in toolbarloader.js.php the styles and scripts from toolbarContainer is dynamically copied to the style and script in the head. After dynamically copying, those should be supposedly removed from toolbarContainer thru responseText.substr. This works well until the last copying of the last style where the removal was "misdirected".

To check that those styles would be redundant if we let it stay is to see that the timeline bars still got styled (in orange bars of varying lengths). Right-clicking on 'Inspect element' you would be that those bars have the class .debug-bar-timeline-** styles with the definition at the bottom.

If any of @rramsey or @kenjis can test this ?

Checklist:

• Securely signed commits

[kenjis]

<style type="text/css">.debu</style> is gone. It is okay.

[kenjis]

@paulbalandan
By the way, your one commit includes more than one change (intent).
In this commit,

• documentation (comment) removal
• refactoring (coding style, variable name change, etc)
• bug fix

In fact, I couldn't figure out what was a real bug fix at first.
If the commit is separated, we could get the intention of code changes,
and our review would be more easily.

[kenjis]

Okay. No <style type="text/css">.debu</style>.

[kenjis]

LGTM