[HttpClient] Fix invalid file

[wkania]

@javiereguiluz, Small fix in your tweaks.

[javiereguiluz]

Thank you @wkania. Although your fix solved the problem, when we only display a PHP code listing, we don't use "configuration blocks". Instead, we use this -> 4e212ee

If a sentence ends with two : then the following indented lines are highlighted as PHP code. That's why we (almost) never have stand-alone .. code-block:: php

[wkania]

Good to know