Update docsting of solve_parameter()

to includ ``simplex_or_intopt`` = "exact_simplex_only".

Author: yuan-zhou

src/sage/numerical/backends/glpk_backend.pyx

@@ -1408,14 +1408,16 @@ cdef class GLPKBackend(GenericBackend):
 
          * - ``simplex_or_intopt``
 
-           - whether to use the ``simplex`` or ``intopt`` routines in
-             GLPK. This is controlled by using ``glp_simplex_only``,
-             ``glp_intopt_only``, and ``glp_simplex_then_intopt``. The latter
-             is useful to deal with a problem in GLPK where problems with no
-             solution hang when using integer optimization; if you specify
-             ``glp_simplex_then_intopt``, sage will try simplex first, then
-             perform integer optimization only if a solution of the LP
-             relaxation exists.
+           - specifiy which of ``simplex``, ``exact`` and ``intopt`` routines
+             in GLPK to use.
+             This is controlled by setting ``simplex_or_intopt`` to
+             ``glp_simplex_only``, ``glp_exact_simplex_only``,
+             ``glp_intopt_only`` and ``glp_simplex_then_intopt``, respectively.
+             The latter is useful to deal with a problem in GLPK where
+             problems with no solution hang when using integer optimization;
+             if you specify ``glp_simplex_then_intopt``,
+             sage will try simplex first, then perform integer optimization
+             only if a solution of the LP relaxation exists.
 
          * - ``verbosity_intopt`` and ``verbosity_simplex``