Texinfo writer: fix spacing bug around HorizontalRule.

Closes #11749.

src/Text/Pandoc/Writers/Texinfo.hs

@@ -241,7 +241,8 @@ blockToTexinfo HorizontalRule =
              text "@end iftex" $$
              text "@ifnottex" $$
              text (replicate 72 '-') $$
-             text "@end ifnottex"
+             text "@end ifnottex" $$
+             blankline
 
 blockToTexinfo (Header 0 _ lst) = do
   txt <- if null lst

test/command/11749.md

@@ -0,0 +1,23 @@
+```
+% pandoc -t texinfo
+Before
+
+----
+
+After
+^D
+@node Top
+@top Top
+
+Before
+
+@iftex
+@bigskip@hrule@bigskip
+@end iftex
+@ifnottex
+------------------------------------------------------------------------
+@end ifnottex
+
+After
+
+```