Remove outdated comments from requirements files

Recent pip no longer requires specific order and can resolve
dependencies automatically.

Also add note to set the right expectation about requirements lower
bounds.

Change-Id: I5a055974c446a7399da93794469cee1120ec63c2
Signed-off-by: Takashi Kajinami <kajinamit@oss.nttdata.com>
3 files changed