bug: revert _available_servers

[cleong14]

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Neovim version (nvim -v)

0.11.0-dev-1652+gf7af919c83

Operating system/version

Darwin 24.2.0

Describe the bug

neovim/nvim-lspconfig - PR #3589 reverts _available_servers back to available_servers causing a nil value error when calling available_servers on nvim startup.

Steps To Reproduce

1. Update nvim-lspconfig and install neoconf.nvim normally
2. Open nvim

Expected Behavior

No error message.

Repro

require("neoconf").setup({
  -- name of the local settings files
  local_settings = ".neoconf.json",
  import = {
    vscode = true,
    coc = true,
    nlsp = false,
  }
})