fix(lsp): revert buf_versions deprecation/replacement (#29217)

* Revert "fix(lsp): account for changedtick version gap on modified reset (#29170)"

This reverts commit 2e6d295f79.

* Revert "refactor(lsp): replace util.buf_versions with changedtick (#28943)"

This reverts commit 5c33815448.

runtime/lua/vim/lsp/_changetracking.lua

@@ -1,5 +1,6 @@
 local protocol = require('vim.lsp.protocol')
 local sync = require('vim.lsp.sync')
+local util = require('vim.lsp.util')
 
 local api = vim.api
 local uv = vim.uv
@@ -276,7 +277,7 @@ local function send_changes(bufnr, sync_kind, state, buf_state)
       client.notify(protocol.Methods.textDocument_didChange, {
         textDocument = {
           uri = uri,
-          version = vim.b[bufnr].changedtick,
+          version = util.buf_versions[bufnr],
         },
         contentChanges = changes,
       })