docs(material/theming): fix typo in theming guide (#25685)
docs(material/theming): fix typo in theming guide (#25685)

In theming guide the mat.get-color-from-palette is shown with a number identifier in quotes, unlike the theming-your-components guide which shows it without quotes.

Fixes angular#25598
angular/components,crisbeto/material2,crisbeto/material2,angular/components,angular/components,crisbeto/material2,crisbeto/material2,angular/components