docs: netlink: clean up after deprecating version

Jiri moved version to legacy specs in commit 0f07415e ("netlink:
specs: don't allow version to be specified for genetlink").
Update the documentation.
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Link: https://lore.kernel.org/r/20231016214540.1822392-1-kuba@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/userspace-api/netlink/genetlink-legacy.rst

@@ -11,6 +11,20 @@ the ``genetlink-legacy`` protocol level.
 Specification
 =============
 
+Globals
+-------
+
+Attributes listed directly at the root level of the spec file.
+
+version
+~~~~~~~
+
+Generic Netlink family version, default is 1.
+
+``version`` has historically been used to introduce family changes
+which may break backwards compatibility. Since compatibility breaking changes
+are generally not allowed ``version`` is very rarely used.
+
 Attribute type nests
 --------------------
 

Documentation/userspace-api/netlink/specs.rst

@@ -86,11 +86,6 @@ name
 Name of the family. Name identifies the family in a unique way, since
 the Family IDs are allocated dynamically.
 
-version
-~~~~~~~
-
-Generic Netlink family version, default is 1.
-
 protocol
 ~~~~~~~~