Remove incorrect usage of :const: in documentation.

Doc/library/decimal.rst

@@ -1294,8 +1294,8 @@ The behavior of Python's comparison operators can be a little surprising where a
 :const:`NaN` is involved.  A test for equality where one of the operands is a
 quiet or signaling :const:`NaN` always returns :const:`False` (even when doing
 ``Decimal('NaN')==Decimal('NaN')``), while a test for inequality always returns
-:const:`True`.  An attempt to compare two Decimals using any of the :const:'<',
-:const:'<=', :const:'>' or :const:'>=' operators will raise the
+:const:`True`.  An attempt to compare two Decimals using any of the ``<``,
+``<=``, ``>`` or ``>=`` operators will raise the
 :exc:`InvalidOperation` signal if either operand is a :const:`NaN`, and return
 :const:`False` if this signal is trapped.  Note that the General Decimal
 Arithmetic specification does not specify the behavior of direct comparisons;