chore: Fix typos in 'compiler' (batch 1)

compiler/rustc_data_structures/src/base_n.rs

@@ -42,7 +42,7 @@ impl fmt::Display for BaseNString {
 }
 
 // This trait just lets us reserve the exact right amount of space when doing fixed-length
-// case-insensitve encoding. Add any impls you need.
+// case-insensitive encoding. Add any impls you need.
 pub trait ToBaseN: Into<u128> {
     fn encoded_len(base: usize) -> usize;