Update week1-05-read-path.md, fix typo (#104)

* Update week1-05-read-path.md, fix typo

* Update week1-04-sst.md

mini-lsm-book/src/week1-05-read-path.md

@@ -27,7 +27,7 @@ src/iterators/two_merge_iterator.rs
 
 You have already implemented a merge iterator that merges iterators of the same type (i.e., memtable iterators). Now that we have implemented the SST formats, we have both on-disk SST structures and in-memory memtables. When we scan from the storage engine, we will need to merge data from both memtable iterators and SST iterators into a single one. In this case, we need a `TwoMergeIterator<X, Y>` that merges two different types of iterators.
 
-You can implement `TwoMergeIterator` in `two_merge_iter.rs`. As we only have two iterators here, we do not need to maintain a binary heap. Instead, we can simply use a flag to indicate which iterator to read. Similar to `MergeIterator`, if the same key is found in both of the iterator, the first iterator takes the precedence.
+You can implement `TwoMergeIterator` in `two_merge_iterator.rs`. As we only have two iterators here, we do not need to maintain a binary heap. Instead, we can simply use a flag to indicate which iterator to read. Similar to `MergeIterator`, if the same key is found in both of the iterator, the first iterator takes the precedence.
 
 ## Task 2: Read Path - Scan