rust: minor documentation spelling fix

Signed-off-by: Trevor Gross <[email protected]>

Author: tgross35

rust/kernel/str.rs

@@ -414,7 +414,7 @@ impl RawFormatter {
     /// If `pos` is less than `end`, then the region between `pos` (inclusive) and `end`
     /// (exclusive) must be valid for writes for the lifetime of the returned [`RawFormatter`].
     pub(crate) unsafe fn from_ptrs(pos: *mut u8, end: *mut u8) -> Self {
-        // INVARIANT: The safety requierments guarantee the type invariants.
+        // INVARIANT: The safety requirements guarantee the type invariants.
         Self {
             beg: pos as _,
             pos: pos as _,