ARROW-7600: [C++][Parquet] failing disabled unittest for nested parquet.
ARROW-7600: [C++][Parquet] failing disabled unittest for nested parquet.

Closes #6218 from emkornfield/nested_parquet and squashes the following commits:

d9baa2b46 <Micah Kornfield> ARROW-7600: failing disabled unittest for nested parquet.

Authored-by: Micah Kornfield <dbc64ab8a675880673029ed6b2cb1d084dfef0bb@gmail.com>
Signed-off-by: François Saint-Jacques <76801b7d5fe2c448a8401d2246372be49d372480@gmail.com>

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