Fix incompatible requirement in lower-constraints

Fix lower-constraints don't match the lower bounds
in the requirements file(s). It causes fail in
requirements-check.

REF:
http://lists.openstack.org/pipermail/openstack-dev/2018-April/129056.html

Change-Id: Iaa3c390d5c66bdbf5836a6d5d59bc5a636235722

lower-constraints.txt

@@ -20,8 +20,8 @@ eventlet==0.18.2
 extras==1.0.0
 fasteners==0.7.0
 fixtures==3.0.0
-flake8==2.5.5
 flake8-import-order==0.12
+flake8==2.5.5
 future==0.16.0
 futurist==1.2.0
 greenlet==0.4.10
@@ -69,8 +69,8 @@ Paste==2.0.2
 PasteDeploy==1.5.0
 pbr==2.0.0
 pep8==1.5.7
-pika==0.10.0
 pika-pool==0.1.3
+pika==0.10.0
 positional==1.2.1
 prettytable==0.7.2
 pyasn1==0.1.8
@@ -94,15 +94,15 @@ pytz==2013.6
 PyYAML==3.12
 reno==2.5.0
 repoze.lru==0.7
+requests-mock==1.2.0
 requests==2.14.2
-requests-mock==1.1.0
 requestsexceptions==1.2.0
 rfc3986==0.3.1
 Routes==2.3.1
 simplejson==3.5.1
 six==1.10.0
 snowballstemmer==1.2.1
-Sphinx==1.6.5
+Sphinx==1.6.2
 sphinxcontrib-websupport==1.0.1
 statsd==3.2.1
 stestr==1.0.0