Docx reader: small change to Fields hyperlink parser

Previously, unquoted string required a space at the end of the
line (and consumed it). Now we either take a space (and don't consume
it), or end of input.

src/Text/Pandoc/Readers/Docx/Fields.hs

@@ -63,7 +63,7 @@ quotedString = do
   concat <$> manyTill inQuotes (try (char '"'))
 
 unquotedString :: Parser String
-unquotedString = manyTill anyChar (try space)
+unquotedString = manyTill anyChar (try $ lookAhead space $> () <|> eof)
 
 fieldArgument :: Parser String
 fieldArgument = quotedString <|> unquotedString