chore(deps) bump resty.mlcache from 2.4.1 to 2.5.0

### Summary

#### [2.5.0]

> Released on: 2020/11/18

##### Added

- `get()` callback functions are now optional. Without a callback, `get()` now
  still performs on-cpu L1/L2 lookups (no yielding). This allows implementing
  new cache lookup patterns guaranteed to be on-cpu for a more constant,
  smoother latency tail end (e.g. values are refreshed in background timers with
  `set()`).
  Thanks Hamish Forbes and Corina Purcarea for proposing this feature and
  participating in its development!
  [#96](thibaultcha/lua-resty-mlcache#96)

##### Fixed

- Improve `update()` robustness to worker crashes. Now, the library behind
  `cache:update()` is much more robust to re-spawned workers when initialized in
  the `init_by_lua` phase.
  [#97](thibaultcha/lua-resty-mlcache#97)
- Document the `peek()` method `stale` argument which was not mentioned, as well
  as the possibility of negative TTL return values for expired items.

kong-2.2.0-0.rockspec

@@ -32,7 +32,7 @@ dependencies = {
   "lua-resty-worker-events == 1.0.0",
   "lua-resty-healthcheck == 1.3.0",
   "lua-resty-cookie == 0.1.0",
-  "lua-resty-mlcache == 2.4.1",
+  "lua-resty-mlcache == 2.5.0",
   "lua-messagepack == 0.5.2",
   "lua-resty-openssl == 0.6.9",
   "lua-resty-counter == 0.2.1",