Remove extra newlines at the beginning/end of files

Those are redundant, and yaml parser strips them in fact. By removing
them, loading and saving yaml file without any change indeed produce the
same output. This is useful for prepare_for_translation.py script (which
adds lang and ref tags) - to produce only change that indeed was made.

developer/code/source-code.md

@@ -10,7 +10,6 @@ ref: 54
 title: Source Code
 ---
 
-
 All the Qubes code is kept in Git repositories. We have divided the project into
 several components, each of which has its own separate repository, for example:
 
@@ -81,4 +80,3 @@ method you choose, you must [sign your code](/doc/code-signing/) before it can b
       name and email, so that *your* name will be used as a commit's author.
    5. Send your patch to `qubes-devel`. Start the message subject with
       `[PATCH]`.
-