Removed a repeated line (#1413)

Signed-off-by: rz-wang <rzwang@umich.edu>

Author: rz-wang

xga/products/relation.py

@@ -152,9 +152,6 @@ def __init__(self, fit_pars: np.ndarray, fit_par_errs: np.ndarray, model_func, x
 
         self._outer_aperture = outer_aperture
 
-        # Store the outer aperture used for the scaling relation (e.g. 'R500' or 300 kpc)
-        self.outer_aperture = outer_aperture
-
         # Again if this relation was generated by XGA then these things will be pased, but we might not have (or want)
         #  the data used to generate scaling relations from literature. If there is data we will check if it has the
         #  correct units