DEP: remove __next__ from Expr (#1169)

* Remove __next__ method from Expr class

The __next__ method was removed from the Expr class, leaving only __iter__ for iteration. This simplifies the class and relies on the iterator protocol of self.terms.

* Update CHANGELOG.md

* Revert "Update CHANGELOG.md"

This reverts commit ebc8cb4.

* Remove __next__ method from Expr class stub

The __next__ method was removed from the Expr class in the type stub file, likely because Expr is not intended to be an iterator. This change improves the accuracy of the type hints.

---------

Co-authored-by: João Dionísio <57299939+Joao-Dionisio@users.noreply.github.com>

Author: Zeroto521

src/pyscipopt/expr.pxi

@@ -202,10 +202,6 @@ cdef class Expr:
     def __iter__(self):
         return iter(self.terms)
 
-    def __next__(self):
-        try: return next(self.terms)
-        except: raise StopIteration
-
     def __abs__(self):
         return abs(buildGenExprObj(self))
 

src/pyscipopt/scip.pyi

@@ -342,7 +342,6 @@ class Expr:
     def __mul__(self, other: Incomplete) -> Incomplete: ...
     def __ne__(self, other: Incomplete)-> Incomplete: ...
     def __neg__(self) -> Incomplete: ...
-    def __next__(self) -> Incomplete: ...
     def __pow__(self, other: Incomplete, mod: Incomplete = ...) -> Incomplete: ...
     def __radd__(self, other: Incomplete) -> Incomplete: ...
     def __rmul__(self, other: Incomplete) -> Incomplete: ...