MinGW 4.3 works for graphviz_test; changed annotation to say that

[SVN r62337]

status/explicit-failures-markup.xml

@@ -1828,7 +1828,8 @@
         </mark-unusable>
         <mark-expected-failures>
           <test name="graphviz_test"/>
-          <toolset name="*mingw*"/>
+          <toolset name="*mingw-4.4*"/>
+          <toolset name="*mingw-4.5*"/>
           <note author="Jeremiah Willcock" refid="49"/>
         </mark-expected-failures>
         <mark-expected-failures>