py312: fix AttributeError doctests (manual changes)

In python 3.12, attribute errors add a suggestion at the end of the
usual error message ("Did you mean ...?").

We add ... at the end of these doctest outputs to fix it.

This commit has a few manual changes which didn't match the sed pattern
in the previous commit.

src/sage/structure/element.pyx

@@ -2856,7 +2856,7 @@ cdef class RingElement(ModuleElement):
             sage: m.is_nilpotent()                                                      # needs sage.modules
             Traceback (most recent call last):
             ...
-            AttributeError: ... object has no attribute 'is_nilpotent'...
+            AttributeError: '...' object has no attribute 'is_nilpotent'...
         """
         if self.is_unit():
             return False

src/sage/symbolic/assumptions.py

@@ -636,7 +636,7 @@ def assume(*args):
         Traceback (most recent call last):
         ...
         AttributeError: 'sage.rings.integer.Integer' object has no
-        attribute 'assume'
+        attribute 'assume'...
 
     Ensure that we can combine the two types of assumptions, as documented::
 

src/sage/symbolic/expression.pyx

@@ -13712,7 +13712,7 @@ cdef get_dynamic_class_for_function(unsigned serial):
         Traceback (most recent call last):
         ...
         AttributeError: 'sage.symbolic.expression.Expression' object has no
-        attribute 'argp1'
+        attribute 'argp1'...
         sage: t = (e + 1).op[0]; t
         tfunc(x)
         sage: t