MAINTAINERS, nilfs2: change project home URLs

MAINTAINERS, nilfs2: change project home URLs

The domain of NILFS project home was changed to "nilfs.sourceforge.io"
to enable https access (the previous domain "nilfs.sourceforge.net" is
redirected to the new one).  Modify URLs of the project home to reflect
this change and to replace their protocol from http to https.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ryusuke Konishi <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>