MD -> LaTeX: Remove the newline in math if not requested

[LecrisUT]

In some styles, the equations are treated as a continuation of the sentence, and in those cases it is desired to not have a new line after the equation, i.e.:

Eisntein's famous equation
:::{math}
E=mc^2,
:::
where $E$ is ...

should be translated like

Eisntein's famous equation
\begin{equation}
E=mc^2,
\end{equation}
where $E$ is ...

(In the current form it makes the subsequent text a new paragraph)

[rowanc1]

Thanks @LecrisUT -- this is a duplicate of #787.