overview-manual: Updated title .PNG file

The file was stretching beyond the rendered display window such
that part of the Yocto Logo was missing.  Also had to place the
updated .PNG file in the mega-manual/figures folder.

(From yocto-docs rev: 5b73c54fcb2c3f60aee2ff7dc19c4aad102aa505)

Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>