minor bugfix in cholla frontend

Previously, the ``domain_right_edge`` attribute of ``ChollaDataset`` was
initialized by assigning it the values of the ``"domain"`` attribute
stored in the hdf5 file. This patch adjusts the logic so that the
``domain_right_edge`` attribute is now the sum of that array and the
array stored in the ``domain_left_edge`` attribute.

yt/frontends/cholla/data_structures.py

@@ -103,7 +103,7 @@ def _parse_parameter_file(self):
             attrs = h5f.attrs
             self.parameters = dict(attrs.items())
             self.domain_left_edge = attrs["bounds"][:].astype("=f8")
-            self.domain_right_edge = attrs["domain"][:].astype("=f8")
+            self.domain_right_edge = self.domain_left_edge + attrs["domain"][:].astype("=f8")
             self.dimensionality = len(attrs["dims"][:])
             self.domain_dimensions = attrs["dims"][:].astype("=f8")
             self.current_time = attrs["t"][:]