ynl: fix schema check errors

Fix two schema check errors that have lurked since the attribute name
validation was made more strict:

not ok 2 conntrack.yaml schema validation
'labels mask' does not match '^[0-9a-z-]+$'

not ok 13 nftables.yaml schema validation
'set id' does not match '^[0-9a-z-]+$'

Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
Link: https://patch.msgid.link/20251127123502.89142-5-donald.hunter@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/netlink/specs/conntrack.yaml

@@ -457,7 +457,7 @@ attribute-sets:
         name: labels
         type: binary
       -
-        name: labels mask
+        name: labels-mask
         type: binary
       -
         name: synproxy

Documentation/netlink/specs/nftables.yaml

@@ -915,7 +915,7 @@ attribute-sets:
         type: string
         doc: Name of set to use
       -
-        name: set id
+        name: set-id
         type: u32
         byte-order: big-endian
         doc: ID of set to use