reduce scope of unsafe blocks

Co-authored-by: Alice Ryhl <aliceryhl@google.com>

src/bytes_mut.rs

@@ -481,15 +481,13 @@ impl BytesMut {
 
         self.reserve(additional);
         let dst = self.spare_capacity_mut().as_mut_ptr();
-        unsafe {
-            // SAFETY: `spare_capacity_mut` returns a valid, properly aligned pointer and we've
-            // reserved enough space to write `additional` bytes.
-            ptr::write_bytes(dst, value, additional);
+        // SAFETY: `spare_capacity_mut` returns a valid, properly aligned pointer and we've
+        // reserved enough space to write `additional` bytes.
+        unsafe { ptr::write_bytes(dst, value, additional) };
 
-            // SAFETY: There are at least `new_len` initialized bytes in the buffer so no
-            // uninitialized bytes are being exposed.
-            self.set_len(new_len);
-        }
+        // SAFETY: There are at least `new_len` initialized bytes in the buffer so no
+        // uninitialized bytes are being exposed.
+        unsafe { self.set_len(new_len) };
     }
 
     /// Sets the length of the buffer.