Update hash table course link

The [Coursera data structures course](https://www.coursera.org/learn/data-structures) covers hash tables in week 4, not week 3.

README.md

@@ -604,7 +604,7 @@ Write code on a whiteboard or paper, not a computer. Test with some sample input
         - [ ] [Supporting Hashing (video)](https://archive.org/details/0102WhatYouShouldKnow/06_04-supportingHashing.mp4)
         - [ ] [Language Support Hash Tables (video)](https://archive.org/details/0102WhatYouShouldKnow/06_05-languageSupportForHashTables.mp4)
         - [ ] [Core Hash Tables (video)](https://www.coursera.org/learn/data-structures-optimizing-performance/lecture/m7UuP/core-hash-tables)
-        - [ ] [Data Structures (video)](https://www.coursera.org/learn/data-structures/home/week/3)
+        - [ ] [Data Structures (video)](https://www.coursera.org/learn/data-structures/home/week/4)
         - [ ] [Phone Book Problem (video)](https://www.coursera.org/learn/data-structures/lecture/NYZZP/phone-book-problem)
         - [ ] distributed hash tables:
             - [Instant Uploads And Storage Optimization In Dropbox (video)](https://www.coursera.org/learn/data-structures/lecture/DvaIb/instant-uploads-and-storage-optimization-in-dropbox)