Fix XML syntax in documentation

Author: petere

doc/src/sgml/fdwhandler.sgml

@@ -381,9 +381,9 @@ GetForeignUpperPaths(PlannerInfo *root,
      that should receive paths representing computation of this step,
      and <literal>input_rel</literal> is the relation representing the input to this
      step.  The <literal>extra</literal> parameter provides additional details,
-     currently, it is set only for <literal>UPPERREL_PARTIAL_GROUP_AGG</>
+     currently, it is set only for <literal>UPPERREL_PARTIAL_GROUP_AGG</literal>
      or <literal>UPPERREL_GROUP_AGG</literal>, in which case it points to a
-     <literal>GroupPathExtraData</> structure.
+     <literal>GroupPathExtraData</literal> structure.
      (Note that <structname>ForeignPath</structname> paths added
      to <literal>output_rel</literal> would typically not have any direct dependency
      on paths of the <literal>input_rel</literal>, since their processing is expected