Fix maxima LaTeX output for matrics

Summary: Maxima tex output generate old code for matrixs(\pmatrix{...} instead of \begin{pmatrix}...\end{pmatrix}). This commit fix it by redifinition a tex function for matrixs. Maybe, it fix bug 387303, but bug report author haven't given a lot of information about this bug and where exectly is the bug.

Test Plan:

1. Run maxima and write matrix([1,2],[3,4]) and check, that there aren't LaTeX output
2. Apply the patch
3. Check, that we have LaTeX matrix in the output

Reviewers: Cantor, asemke

Reviewed By: Cantor, asemke

Subscribers: Cantor, KDE Edu

Tags: KDE Edu, Cantor

Differential Revision: https://phabricator.kde.org/D12712