Natural Selection - publish 1.6 with PhET-iO fixes

[pixelzoom]

The PhET-iO version of Natural Selection 1.5 has a serious problem, which has been fixed in main but not republished. See #362 for details.

@brent-phet noted in #362 (comment) that the 1.5 PhET-iO version is getting "significant traffic outside of PhET".

@zepumph said in #362 (comment):

Today during PhET-iO meeting, we decided that the best course of action is to publish 1.6 with the fix. This will allow a facility for migrating old, buggy states into the new version. This doesn't mean that this is top priority for an upcoming iteration, but we will work its way into planning.

When this is a priority, it would probably be good to have @pixelzoom and @zepumph review the migration rule for populating the recessiveMutatants to make sure it will well for current Standard Wrappers.

[brent-phet]

Based on planning meeting with @kathy-phet and @marlitas, this has been scheduled to start on September 9 as part of Iteration F2, due to availability and the focus on current sims in development.

[pixelzoom]

Unassigning myself until this work is scheduled for an iteration.