🚨 roles: nfs_host: Rename

Roles names are expected to be lower case with underscores only,
see ansible-lint warning:

    % ansible-lint -t role-name
    WARNING  Listing 1 violation(s) that are fatal
    role-name: Role name nfs-host does not match ``^[a-z][a-z0-9_]*$`` pattern.
    roles/nfs-host:1

    Read documentation for instructions on how to ignore specific rule violations.

                 Rule Violation Summary
     count tag       profile rule associated tags
         1 role-name basic   deprecations, metadata

    Failed after min profile: 1 failure(s), 0 warning(s) on 135 files.

Fixes: 2138870520 ("nfs server wird nicht im k3s laufen, labeling entfernt")

host-plumbum.yml

@@ -3,7 +3,7 @@
   become: true
 
   roles:
-    - role: nfs-host
+    - role: nfs_host
       vars:
         nfs_host_exports:
           - directory: "/srv/nfs/backup"

roles/nfs_host/defaults/main.yml

@@ -1,4 +1,4 @@
-# Defaults for nfs-host
+# Defaults for nfs_host
 ---
 nfs_host_exports: []
   # - directory: "/srv/nfs"