Remove usage of m_inst in MultiIndexableTester #38
Description
m_inst refers to the first instance of the MultiIndexable being tested, and it is generated by calling make[0]. However, there are no special differences between the first and subsequent elements returned by make, and thus every test of m_inst should actually be a test of each element from make. I'm not sure why I wrote those tests to use m_inst, but a lot of them were written at 8am on a city bus so I'll cut myself some slack :^)