Markdown reader: when splitting pipe table cells, skip tex math.

You might have a `|` character inside math.
(Or for that matter something that the parser might mistake
for raw HTML.)

See #3481.

src/Text/Pandoc/Readers/Markdown.hs

@@ -1401,7 +1401,7 @@ pipeTableRow = try $ do
   skipMany spaceChar
   openPipe <- (True <$ char '|') <|> return False
   -- split into cells
-  let chunk = void (code <|> rawHtmlInline <|> escapedChar <|> rawLaTeXInline')
+  let chunk = void (code <|> math <|> rawHtmlInline <|> escapedChar <|> rawLaTeXInline')
        <|> void (noneOf "|\n\r")
   let cellContents = ((trim . snd) <$> withRaw (many chunk)) >>=
         parseFromString pipeTableCell