Fix typo in train split name (#3751)

* Fix typo in README guide

* Fix split naming and table alignment in README guide

* Fix split naming and table alignment in all datasets

* Fix previously malformed dataset cards

* Fix previously malformed dataset cards

Commit from https://github.com/huggingface/datasets/commit/af6e54febe3b822118dfed28ddb797d8350e5d27

README.md

@@ -88,9 +88,9 @@ Kannada
 
 ### Data Splits
 
-|              | Tain   | Valid | Test |
-| -----        | ------: | -----: | ----:|
-| Kannada    |  4941  | 618  | 617 |
+|         | train | validation | test |
+|---------|------:|-----------:|-----:|
+| Kannada |  4941 |        618 |  617 |
 
 ## Dataset Creation