fix(api): deprecate nvim_subscribe, nvim_unsubscribe #30456

Problem:
- nvim_subscribe, nvim_unsubscribe were deprecated in
  aec4938a21a02d279d13a9eb64ef3b7cc592c374 but this wasn't set in the
  API metadata.
- The function annotations
  ```
  FUNC_API_SINCE(1) FUNC_API_REMOTE_ONLY FUNC_API_DEPRECATED_SINCE(13)
  ```
  cause this test to fail:
   ```
   RUN T3 api metadata functions are compatible with old metadata or have new level: 3.00 ms ERR
   test/functional/api/version_spec.lua:135: function vim_subscribe was removed but exists in level 0 which nvim should be compatible with
   stack traceback:
     test/functional/api/version_spec.lua:135: in function <test/functional/api/version_spec.lua:128>
   ```

Solution:
- Set the API metadata.
- Rearrange the annotations so that FUNC_API_DEPRECATED_SINCE is 2nd:
  ```
  FUNC_API_SINCE(1) FUNC_API_DEPRECATED_SINCE(13) FUNC_API_REMOTE_ONLY
  ```

1 files changed, 5 insertions, 0 deletions

diff --git a/src/nvim/generators/c_grammar.lua b/src/nvim/generators/c_grammar.lua
index 9b1c284c1e..890c260843 100644
--- a/src/nvim/generators/c_grammar.lua
+++ b/src/nvim/generators/c_grammar.lua
@@ -257,6 +257,11 @@ if arg[1] == '--test' then
     'char *xstpcpy(char *restrict dst, const char *restrict src) {}',
     'bool try_leave(const TryState *const tstate, Error *const err) {}',
     'void api_set_error(ErrorType errType) {}',
+    {
+      'void nvim_subscribe(uint64_t channel_id, String event)',
+      'FUNC_API_SINCE(1) FUNC_API_DEPRECATED_SINCE(13) FUNC_API_REMOTE_ONLY',
+      '{}',
+    },
 
     -- Do not consume leading preproc statements
     {