braketbar=true in output

Issue Summary

The custom attribute used in

https://github.com/mathjax/MathJax-src/blob/develop/ts/input/tex/braket/BraketMethods.ts#L85

appears in SVG and HTML output, creating invalid markup.

Steps to Reproduce:

• Visit https://www.mathjax.org/#demo
• Paste $\set{c_{i,j}| i \in I, j \in J}$
• check DOM to find | output having braketbar="true"