remove newline when exporting highlight to My Clipping

frontend/apps/reader/modules/readerhighlight.lua

@@ -372,7 +372,8 @@ function ReaderHighlight:exportToClippings(page, item)
         clippings:write(self.document.file:gsub("(.*/)(.*)", "%2").."\n")
         clippings:write("- Koreader Highlight Page "..page.." ")
         clippings:write("| Added on "..os.date("%A, %b %d, %Y %I:%M:%S %p\n\n"))
-        clippings:write(item["text"].."\n")
+        -- My Clippings only holds one line of highlight
+        clippings:write(item["text"]:gsub("\n", " ").."\n")
         clippings:write("==========\n")
         clippings:close()
         os.setlocale(current_locale)