rename allocating-fips to managing-fips, fix links

...enstack/docs/additional-information/virtual-networking.md

...ack/docs/getting-started/creating-first-infrastructure.md

...mpute/openstack/docs/how-to-guides/accessing-instances.md

topics/compute/openstack/docs/how-to-guides/create-router.md

...ute/openstack/docs/how-to-guides/managing-floating-ips.md

...penstack/docs/technical-reference/brno-site/networking.md

topics/compute/openstack/mkdocs.yml