Add compat note for OncePer types (#58716)

Closes #58703

Author: jakobnissen

base/lock.jl

@@ -704,6 +704,9 @@ calls in the same process will return exactly the same value. This is useful in
 code that will be precompiled, as it allows setting up caches or other state
 which won't get serialized.
 
+!!! compat "Julia 1.12"
+    This type requires Julia 1.12 or later.
+
 ## Example
 
 ```jldoctest
@@ -814,6 +817,9 @@ if that behavior is correct within your library's threading-safety design.
 
 See also: [`OncePerTask`](@ref).
 
+!!! compat "Julia 1.12"
+    This type requires Julia 1.12 or later.
+
 ## Example
 
 ```jldoctest
@@ -942,6 +948,9 @@ exactly once per Task. All future calls in the same Task will return exactly the
 
 See also: [`task_local_storage`](@ref).
 
+!!! compat "Julia 1.12"
+    This type requires Julia 1.12 or later.
+
 ## Example
 
 ```jldoctest