one clippy lint having a rough one today

bunch of new bugs in https://github.com/rust-lang/rust-clippy/issues?q=is%3Aissue+let_underscore_untyped
our use seems perfectly fine, what clippy wanted was nonsense:

```
error: non-binding `let` without a type annotation
  --> kube-runtime/src/reflector/store.rs:87:12
   |
87 | pub struct Store<K: 'static + Resource>
   |            ^^^^^
   |
   = help: consider adding a type annotation or removing the `let` keyword
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#let_underscore_untyped

error: non-binding `let` without a type annotation
   --> kube-runtime/src/watcher.rs:123:5
    |
123 |     InitListed { resource_version: String },
    |     ^^^^^^^^^^
    |
    = help: consider adding a type annotation or removing the `let` keyword
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#let_underscore_untyped
```

Signed-off-by: clux <sszynrae@gmail.com>

Author: clux

kube-runtime/src/lib.rs

@@ -16,6 +16,8 @@
 #![allow(clippy::type_repetition_in_bounds)]
 // Triggered by Tokio macros
 #![allow(clippy::semicolon_if_nothing_returned)]
+// Triggered by nightly clippy on idiomatic code
+#![allow(clippy::let_underscore_untyped)]
 
 pub mod controller;
 pub mod events;