build(deps): bump unibilium to v2.1.4

Build system adaptations to upstream changes:

* added `build.zig`
* `CMakeLists.txt` with (opt-out) support for docs, tests, tools
  (disabled)

scripts/bump_deps.lua

@@ -32,7 +32,6 @@ local zig_mode = {
   uncrustify = false,
   wasmtime = false,
   libuv = false,
-  unibilium = 'nested',
   utf8proc = 'nested',
 }