src/sage/interfaces/maxima_lib.py: update some integration doctests

There are some tests in this file that still mention abs_integrate,
though it was disabled a few years ago. We remove all mention of it,
and clean up a bit:

  * Drop a test repeated in src/sage/symbolic/integration/integral.py
  * Remove "# known bug" from any examples that now pass without
    abs_integrate
  * Delete any remaining "# known bug" tests. They are not really bugs
    -- you just don't get a nice answer -- and it is a waste of time to
    run them and then throw away the answer.

Author: orlitzky

src/sage/interfaces/maxima_lib.py

@@ -726,58 +726,21 @@ def sr_integral(self, *args):
             sage: assumptions()  # Check the assumptions really were forgotten
             []
 
-        Make sure the abs_integrate package is being used,
-        :issue:`11483`. The following are examples from the Maxima
-        abs_integrate documentation::
+        An example from the maxima documentation involving the
+        absolute value::
 
-            sage: integrate(abs(x), x)
-            1/2*x*abs(x)
-
-        ::
-
-            sage: integrate(sgn(x) - sgn(1-x), x)  # known bug
+            sage: integrate(sgn(x) - sgn(1-x), x)
             abs(x - 1) + abs(x)
 
-        This is a known bug in Sage symbolic limits code, see
+        This is a fixed bug in Sage symbolic limits code, see
         :issue:`17892` and https://sourceforge.net/p/maxima/bugs/3237/ ::
 
-            sage: integrate(1 / (1 + abs(x-5)), x, -5, 6) # not tested -- known bug
+            sage: integrate(1 / (1 + abs(x-5)), x, -5, 6)
             log(11) + log(2)
 
-        ::
-
-            sage: integrate(1/(1 + abs(x)), x)  # known bug
-            1/2*(log(x + 1) + log(-x + 1))*sgn(x) + 1/2*log(x + 1) - 1/2*log(-x + 1)
-
-        ::
-
-            sage: integrate(cos(x + abs(x)), x)  # known bug
-            -1/2*x*sgn(x) + 1/4*(sgn(x) + 1)*sin(2*x) + 1/2*x
-
-        The last example relies on the following simplification::
-
-            sage: maxima("realpart(signum(x))")
-            signum(x)
-
-        An example from sage-support thread e641001f8b8d1129::
-
-            sage: f = e^(-x^2/2)/sqrt(2*pi) * sgn(x-1)
-            sage: integrate(f, x, -Infinity, Infinity)  # known bug
-            -erf(1/2*sqrt(2))
-
-        From :issue:`8624`::
-
-            sage: integral(abs(cos(x))*sin(x),(x,pi/2,pi))
-            1/2
-
-        ::
-
-            sage: integrate(sqrt(x + sqrt(x)), x).canonicalize_radical()  # known bug
-            1/12*((8*x - 3)*x^(1/4) + 2*x^(3/4))*sqrt(sqrt(x) + 1) + 1/8*log(sqrt(sqrt(x) + 1) + x^(1/4)) - 1/8*log(sqrt(sqrt(x) + 1) - x^(1/4))
-
         And :issue:`11594`::
 
-            sage: integrate(abs(x^2 - 1), x, -2, 2)  # known bug
+            sage: integrate(abs(x^2 - 1), x, -2, 2)
             4
 
         This definite integral returned zero (incorrectly) in at least