third party: Upgrade rustc_hash

Summary:
To 2.1

Unfortunately, I can't remove the old version of the crate. The problem is that it appears in the [public API](https://docs.rs/tiktoken-rs/latest/tiktoken_rs/struct.CoreBPE.html#method.new) of `tiktoken_rs`, which we also import. That crate has a PR to upgrade its dependency [here](zurawiki/tiktoken-rs#95) but that has not been merged. Alternatives here are:

 1. Fork `tiktoken_rs`. This seems worse.
 2. It's strictly speaking possible to use generics combined with some other tricks to avoid needing to name v1 of `FxHashMap` in fbsource. However, that makes that code extraordinarily hard to change and work with, and doesn't seem all that clearly motivated.

If there's something else I should be doing here, all ears

Reviewed By: zertosh

Differential Revision: D68064854

fbshipit-source-id: bd1c96abbc0ebaa178a55826bc85c61eb35e8301

Author: JakobDegen

Cargo.toml

@@ -248,7 +248,7 @@ ref-cast = "1.0.0"
 regex = "1.5.4"
 relative-path = { version = "1.7.0", features = ["serde"] }
 rusqlite = { version = "0.29.0", features = ["bundled"] }
-rustc-hash = { version = "1.1" }
+rustc-hash = { version = "2.1" }
 rustls = "0.21.5"
 rustls-native-certs = { package = "rustls-native-certs", version = "0.6.2" }
 rustls-pemfile = { package = "rustls-pemfile", version = "1.0.0" }

shim/third-party/rust/Cargo.toml

@@ -171,7 +171,7 @@ regex = "1.5.4"
 relative-path = { version = "1.7.0", features = ["serde"] }
 ring = "=0.17.5" # Upgrading this is possible, but a pain, so we don't want to pick up every new minor version
 rusqlite = { version = "0.29.0", features = ["bundled"] }
-rustc-hash = "1.1.0"
+rustc-hash = "2.1.0"
 rustls = "0.21.0"
 rustls-native-certs = { package = "rustls-native-certs", version = "0.6.2" }
 rustls-pemfile = { package = "rustls-pemfile", version = "1.0.0" }