sage.symbolic.ring: Remove function deprecated in sagemath#32665 (2021)

src/sage/symbolic/ring.pyx

@@ -1301,33 +1301,6 @@ def the_SymbolicRing():
     return SR
 
 
-def is_SymbolicExpressionRing(R):
-    """
-    Return True if ``R`` is the symbolic expression ring.
-
-    This function is deprecated.  Instead, either use ``R is SR`` (to
-    test whether ``R`` is the unique symbolic ring ``SR``); or
-    ``isinstance`` with :class:`~sage.rings.abc.SymbolicRing`
-    (when also symbolic subrings and callable symbolic rings should
-    be accepted).
-
-    EXAMPLES::
-
-        sage: from sage.symbolic.ring import is_SymbolicExpressionRing
-        sage: is_SymbolicExpressionRing(ZZ)
-        doctest:warning...
-        DeprecationWarning: is_SymbolicExpressionRing is deprecated;
-        use "... is SR" or isinstance(..., sage.rings.abc.SymbolicRing instead
-        See https://github.com/sagemath/sage/issues/32665 for details.
-        False
-        sage: is_SymbolicExpressionRing(SR)
-        True
-    """
-    from sage.misc.superseded import deprecation
-    deprecation(32665, 'is_SymbolicExpressionRing is deprecated; use "... is SR" or isinstance(..., sage.rings.abc.SymbolicRing instead')
-    return R is SR
-
-
 def var(name, **kwds):
     """
     EXAMPLES::