Remove deprecated LIBVIRT_LXC_NOSECLABEL env var (#77426)

Fixes #77395

changelogs/fragments/77395-remove-libvirt_lxc_noseclabel.yml

@@ -0,0 +1,2 @@
+removed_features:
+  - Remove deprecated ``LIBVIRT_LXC_NOSECLABEL`` environment variable (https://github.com/ansible/ansible/issues/77395)

lib/ansible/config/base.yml

@@ -784,11 +784,6 @@ DEFAULT_LIBVIRT_LXC_NOSECLABEL:
     - "This setting causes libvirt to connect to lxc containers by passing --noseclabel to virsh.
       This is necessary when running on systems which do not have SELinux."
   env:
-  - name: LIBVIRT_LXC_NOSECLABEL
-    deprecated:
-      why: environment variables without ``ANSIBLE_`` prefix are deprecated
-      version: "2.12"
-      alternatives: the ``ANSIBLE_LIBVIRT_LXC_NOSECLABEL`` environment variable
   - name: ANSIBLE_LIBVIRT_LXC_NOSECLABEL
   ini:
   - {key: libvirt_lxc_noseclabel, section: selinux}