FIX: Fix a typo in a comment

Author: bluss

src/lib.rs

@@ -543,7 +543,7 @@ impl<A: Array> ArrayVec<A> {
         // Memory safety
         //
         // When the Drain is first created, it shortens the length of
-        // the source vector to make sure no uninitalized or moved-from elements
+        // the source vector to make sure no uninitialized or moved-from elements
         // are accessible at all if the Drain's destructor never gets to run.
         //
         // Drain will ptr::read out the values to remove.