gen_vimdoc.py: mpack: collect functions in 1 dict

All Nvim API, core Vimscript, and core Lua functions are globally
unique, so there is no need for per-module nested dicts.

BEFORE (generated mpack structure):
    [
      {
        "buffer.c": {
          "nvim__buf_stats": { ... },
          ...
        },
        "window.c": {
          "nvim_win_close": { ... },
          ...
        },
        ...
      }
    ]

AFTER (generated mpack structure):
    [
      {
        "nvim__buf_stats": {
          ...
        },
        "nvim_buf_attach": {
          ...
        },
        "nvim_tabpage_set_var": {
          ...
        },
        "nvim_ui_attach": {
          ...
        },
        "nvim_win_close": {
          ...
        }
      }
    ]

0 files changed, 0 insertions, 0 deletions