Update PhET-iO grunt production comment to assign to @brent-phet instead of @kathy-phet

[brent-phet]

https://github.com/phetsims/perennial/blob/9e8f1fcf245427f16953190e8f8155aef0efdbf6/js/grunt/production.js#L224

From grunt production --branch=1.3 --brands=phet,phet-io:

PhET-iO deploys involve a couple of extra steps after production. Please ensure the following are accomplished: ...

2. Create an issue in the phet-io repo and assign to @kathy-phet to update the main "PhET-iO Simulations" spreadsheet from this new publication. (https://docs.google.com/spreadsheets/d/18_QNGuVtYtxOEKG9xRBs_PSQpyvzySF1Gk5puR-5Fv4/edit#gid=1881767354)

[brent-phet]

This is a duplicate to #325 resolved by @pixelzoom. @kathy-phet just mentioned assigning @zepumph but not strictly required.

[brent-phet]

Closing.