MAINT: remove deepcopy functionality

Was only ever being used unintentionally in the tests and doesn't really
make sense. Use .clone() instead

Author: mjsir911

pypdf/generic/_base.py

@@ -283,9 +283,6 @@ def indirect_reference(self) -> "IndirectObject":  # type: ignore[override]
     def get_object(self) -> Optional["PdfObject"]:
         return self.pdf.get_object(self)
 
-    def __deepcopy__(self, memo: Any) -> "IndirectObject":
-        return IndirectObject(self.idnum, self.generation, self.pdf)
-
     def _get_object_with_check(self) -> Optional["PdfObject"]:
         o = self.get_object()
         # the check is done here to not slow down get_object()