Replace git.openstack.org URLs with opendev.org URLs

1. Replace git.openstack.org URLs with opendev.org URLs
2. Remove the unnecessary "=" from some files

Change-Id: I86ad7f5d51d2b82b39aa8bebb34dfffc54df6939

HACKING.rst

@@ -1,4 +1,4 @@
 os-resource-classes Style Commandments
-===============================================
+======================================
 
 Read the OpenStack Style Commandments https://docs.openstack.org/hacking/latest/

README.rst

@@ -1,6 +1,6 @@
-===============================
+===================
 os-resource-classes
-===============================
+===================
 
 A list of standardized resource classes for OpenStack.
 
@@ -20,7 +20,7 @@ custom resource class always begins with a ``CUSTOM_`` prefix.
 
 * Free software: Apache license
 * Documentation: https://docs.openstack.org/os-resource-classes/latest
-* Source: https://git.openstack.org/cgit/openstack/os-resource-classes
+* Source: https://opendev.org/openstack/os-resource-classes
 * Bugs: https://storyboard.openstack.org/#!/project/openstack/os-resource-classes
 
 .. _placement API: https://developer.openstack.org/api-ref/placement/

tox.ini

@@ -18,7 +18,7 @@ setenv =
    OS_STDERR_CAPTURE=1
    OS_TEST_TIMEOUT=60
 deps =
-  -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt}
+  -c{env:UPPER_CONSTRAINTS_FILE:https://opendev.org/openstack/requirements/raw/branch/master/upper-constraints.txt}
   -r{toxinidir}/test-requirements.txt
 commands = stestr run {posargs}
 
@@ -40,7 +40,7 @@ commands =
 
 [testenv:docs]
 deps =
-  -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt}
+  -c{env:UPPER_CONSTRAINTS_FILE:https://opendev.org/openstack/requirements/raw/branch/master/upper-constraints.txt}
   -r{toxinidir}/doc/requirements.txt
 commands = sphinx-build -W -b html doc/source doc/build/html