Allow clippy::unnecessary_fallible_conversions

FFI types like `c_long` vary on 32/64-bit, and the check is only needed on
64-bit conversions. Fixing this lint makes the code less readable.

```
error: use of a fallible conversion when an infallible one could be used
   --> external/uwb/src/rust/uwb_core/src/uci/uci_manager.rs:895:60
    |
895 | ...                   Some(u16size) => match u16size.try_into() {
    |                                                      ^^^^^^^^ help: use: `into`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_fallible_conversions
    = note: `-D clippy::unnecessary-fallible-conversions` implied by `-D warnings`
    = help: to override `-D warnings` add
`#[allow(clippy::unnecessary_fallible_conversions)]`
```

Bug: http://b/321303117
Test: toolchain/android_rust/test_compiler.py --prebuilt-path dist/rust-dev.tar.xz --target aosp_cf_x86_64_phone --all-rust
Change-Id: I26bb78f63c2205003aa0656d77ed86b4c62a4ba7
1 file changed
tree: 008572c330b5bfda51061157d4b397a86998eb2f
  1. src/
  2. .gitignore
  3. Android.bp
  4. DIR_METADATA
  5. METADATA
  6. MODULE_LICENSE_APACHE2
  7. NOTICE
  8. OWNERS
  9. OWNERS_chromeos
  10. PREUPLOAD.cfg