Temporarily disable capa name masking

There is a bug I need to fix when a student re-visits a problem that they
had solved previously without masking enabled, their old state does not
load correclty.

It's simplest to turn off masking now, and re-enable it with the whole fix.

Masking only applies when problems use the new shuffle="true" or answer-pool features,
probably not used outside of Stanford yet. If a problem with masking is saved by a student,
then this change will prevent that problem from loading for that student,
so idealy make this change when no masked problems have been used.

Masked problems otherwise work as documented with
this change, they just will not use masking internally.

The change here is a small deletion to remove the masking=True logic, and more
lengthy changes to remove the tests of masking.