Fix outdated notes in requirement files

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

Also add a note to explain that lower bounds of requirements are no
longer tested and these are now maintained on best-effort-basis.

Change-Id: I8287f379cb8d17254df8064af69279fe3361e7a4

Author: kajinamit

doc/requirements.txt

@@ -1,6 +1,3 @@
-# The order of packages is significant, because pip processes them in the order
-# of appearance. Changing the order has an impact on the overall integration
-# process, which may cause wedges in the gate later.
 # These are needed for docs generation
 openstackdocstheme>=2.2.1 # Apache-2.0
 reno>=3.2.0 # Apache-2.0

requirements.txt

@@ -1,6 +1,6 @@
-# The order of packages is significant, because pip processes them in the order
-# of appearance. Changing the order has an impact on the overall integration
-# process, which may cause wedges in the gate later.
+# Requirements lower bounds listed here are our best effort to keep them up to
+# date but we do not test them so no guarantee of having them all correct. If
+# you find any incorrect lower bounds, let us know or propose a fix.
 pbr>=5.5.0 # Apache-2.0
 PrettyTable>=0.7.2 # BSD
 keystoneauth1>=5.0.0 # Apache-2.0

test-requirements.txt

@@ -1,8 +1,4 @@
-# The order of packages is significant, because pip processes them in the order
-# of appearance. Changing the order has an impact on the overall integration
-# process, which may cause wedges in the gate later.
 # Hacking already pins down pep8, pyflakes and flake8
-
 hacking>=7.0.0,<7.1.0 # Apache-2.0
 flake8-import-order # LGPLv3
 docutils>=0.16