[Minor] Misc cleanup docs and uneeded test `use

arrow/README.md

@@ -117,7 +117,7 @@ it relies heavily on LLVM auto-vectorisation to achieve this. Unfortunately the
 particularly for x86_64, favour portability over performance, and LLVM will consequently avoid
 using more recent instructions that would result in errors on older CPUs.
 
-To address this it is recommended that you specify the override the LLVM defaults either
+To address this it is recommended that you override the LLVM defaults either
 by setting the `RUSTFLAGS` environment variable, or by setting `rustflags` in your
 [Cargo configuration](https://doc.rust-lang.org/cargo/reference/config.html)
 

parquet/src/util/bit_pack.rs

@@ -97,7 +97,6 @@ unpack!(unpack64, u64, 8, 64);
 #[cfg(test)]
 mod tests {
     use super::*;
-    use rand::{thread_rng, Rng};
 
     #[test]
     fn test_basic() {