* Update adjust-the-height-of-an-element-using-the-height-property.spanish.md
* Updated test text to Spanish
And changed CSS rule back to English in the example. Using back-ticks to properly format the code block
Added some missing words and gave a better translation to rgba meanning, because people could be asking why b is Azul, instead of saying that is blue and then placing the translation to spanish Azul.