remove now unused require for matrixmarket
remove now unused require for matrixmarket

The code that depended on matrixmarket has been removed in c23761be but
I forgot to remove the `require()` in that commit.

josdejong/mathjs,josdejong/mathjs,josdejong/mathjs,FSMaxB/mathjs,josdejong/mathjs,FSMaxB/mathjs,josdejong/mathjs,FSMaxB/mathjs,FSMaxB/mathjs,FSMaxB/mathjs