Delete added_examples directory

[OliviaLynn]

Problem & Solution Description (including issue #)

Removing the example notebook as part of LSSTDESC/rail#48

Notebook is now available within the umbrella rail package at https://github.com/LSSTDESC/rail/blob/main/examples/estimation_examples/GPz_estimation_example.ipynb

Code Quality

• My code follows the code style of this project
• I have written unit tests or justified all instances of #pragma: no cover; in the case of a bugfix, a new test that breaks as a result of the bug has been added
• My code contains relevant comments and necessary documentation for future maintainers; the change is reflected in applicable demos/tutorials (with output cleared!) and added/updated docstrings use the NumPy docstring format
• Any breaking changes, described above, are accompanied by backwards compatibility and deprecation warnings

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (a26b66c) 64.11% compared to head (8f2c6d1) 64.11%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #13   +/-   ##
=======================================
  Coverage   64.11%   64.11%           
=======================================
  Files           2        2           
  Lines         510      510           
=======================================
  Hits          327      327           
  Misses        183      183           

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[drewoldag]

Approved!