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

Change-Id: I1fa55fdb52f2a74e01c28268dd3973e3151ef7e3
Closes-Bug: #1825923

README.rst

@@ -17,7 +17,7 @@ For more details, see the `OpenStack Documentation Contributor Guide
 <https://docs.openstack.org/contributor-guide/>`_.
 
 * License: Apache License, Version 2.0
-* Source: https://git.openstack.org/cgit/openstack/openstack-doc-tools
+* Source: https://opendev.org/openstack/openstack-doc-tools
 * Bugs: https://bugs.launchpad.net/openstack-doc-tools
 
 Prerequisites

tox.ini

@@ -9,7 +9,7 @@ install_command = pip install {opts} {packages}
 # Install also sitemap scraping tool, not installed by default
 # therefore not in requirements file
 deps = scrapy>=1.0.0
-       -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
        -r{toxinidir}/requirements.txt
 commands = stestr run --slowest {posargs}