fix: Avoid hard coded length in doc example
@@ -27,7 +27,7 @@ use std::u64;
/// # let data_len = buf.len();
/// # let r = Cursor::new(buf);
///
-/// let reader = TSMReader::try_new(BufReader::new(r), 4_222_248).unwrap();
+/// let reader = TSMReader::try_new(BufReader::new(r), data_len).unwrap();
///
/// // reader allows you to access each index entry, and each block for each
/// // entry in order.
