JATS writer: don't use break element for LineBreak.

It's only allowed in a few special contexts, and not in
p elements.

src/Text/Pandoc/Writers/JATS.hs

@@ -390,7 +390,8 @@ inlineToJATS _ il@(RawInline f x)
   | otherwise   = do
       report $ InlineNotRendered il
       return empty
-inlineToJATS _ LineBreak = return $ selfClosingTag "break" []
+inlineToJATS _ LineBreak = return cr -- not allowed as child of p
+-- see https://jats.nlm.nih.gov/publishing/tag-library/1.2/element/break.html
 inlineToJATS _ Space = return space
 inlineToJATS opts SoftBreak
   | writerWrapText opts == WrapPreserve = return cr

test/writer.jats

@@ -68,7 +68,8 @@ Gruber’s markdown test suite.</p>
   item. Because a hard-wrapped line in the middle of a paragraph looked like a
   list item.</p>
   <p>Here’s one with a bullet. * criminey.</p>
-  <p>There should be a hard line break<break />here.</p>
+  <p>There should be a hard line break
+  here.</p>
 </sec>
 <sec id="block-quotes">
   <title>Block Quotes</title>