remove FreeBSD xfail decorator from TestCallStdStringFunction

This test is consistently reporting unexpected pass for me on FreeBSD
10 and 12. It was failing on the old FreeBSD buildbot which has now been
retired for some time. Will investigate further if this fails once a new
buildbot is configured and running tests.

llvm.org/pr17807

llvm-svn: 310626

lldb/packages/Python/lldbsuite/test/expression_command/call-function/TestCallStdStringFunction.py

@@ -26,9 +26,6 @@ class ExprCommandCallFunctionTestCase(TestBase):
     @expectedFailureAll(
         compiler="icc",
         bugnumber="llvm.org/pr14437, fails with ICC 13.1")
-    @expectedFailureAll(
-        oslist=['freebsd'],
-        bugnumber='llvm.org/pr17807 Fails on FreeBSD buildbot')
     @expectedFailureAll(oslist=["windows"], bugnumber="llvm.org/pr21765")
     def test_with(self):
         """Test calling std::String member function."""