Fix ignored continued=false in parse()

This fixes a situation where the continued=false option in parse() was
ignored during notebook export.

src/Literate.jl

@@ -78,6 +78,7 @@ function parse(content; allow_continued = true)
         end
     end
 
+    if allow_continued
         # find code chunks that are continued
         last_code_chunk = 0
         for (i, chunk) in enumerate(chunks)
@@ -90,6 +91,7 @@ function parse(content; allow_continued = true)
             end
             last_code_chunk = i
         end
+    end
 
     # if we don't allow continued code blocks we need to merge MDChunks into the CodeChunks
     if !allow_continued