chore: Remove unused base16 dependency and dead hex wrapper funct…

…ion (vercel/turborepo#8207)

### Description

Noticed these dependencies/functions were unused.

For the most part, it's better to do these conversions with the built-in
`format!()`.

Parsing base16 could make sense for this as a dependency, but we're not
doing that.

### Testing Instructions

```
cargo check
```

Also grepped through next.js to check that we're not using it there.

crates/turbo-tasks-hash/Cargo.toml

@@ -13,8 +13,6 @@ bench = false
 workspace = true
 
 [dependencies]
-base16 = "0.2.1"
-hex = "0.4.3"
 md4 = "0.10.1"
 turbo-tasks-macros = { workspace = true }
 twox-hash = "1.6.3"

crates/turbo-tasks-hash/src/hex.rs

@@ -2,8 +2,3 @@
 pub fn encode_hex(n: u64) -> String {
     format!("{:01$x}", n, std::mem::size_of::<u64>() * 2)
 }
-
-/// Encodes a byte slice into a hex string.
-pub fn encode_hex_string(bytes: &[u8]) -> String {
-    hex::encode(bytes)
-}

crates/turbo-tasks-hash/src/lib.rs

@@ -4,16 +4,14 @@
 //! invalidation, and encoding the hash to an hexadecimal string for use in a
 //! file name.
 
-mod base16;
 mod deterministic_hash;
 mod hex;
 mod md4;
 mod xxh3_hash64;
 
 pub use crate::{
-    base16::encode_base16,
     deterministic_hash::{DeterministicHash, DeterministicHasher},
-    hex::{encode_hex, encode_hex_string},
+    hex::encode_hex,
     md4::hash_md4,
     xxh3_hash64::{hash_xxh3_hash64, Xxh3Hash64Hasher},
 };