Finish conversion of REALM doc to MDX

docs/source/model_doc/realm.mdx

@@ -14,8 +14,7 @@ specific language governing permissions and limitations under the License.
 
 ## Overview
 
-The REALM model was proposed in `REALM: Retrieval-Augmented Language Model Pre-Training
-<https://arxiv.org/abs/2002.08909>`__ by Kelvin Guu, Kenton Lee, Zora Tung, Panupong Pasupat and Ming-Wei Chang. It's a
+The REALM model was proposed in [REALM: Retrieval-Augmented Language Model Pre-Training](https://arxiv.org/abs/2002.08909) by Kelvin Guu, Kenton Lee, Zora Tung, Panupong Pasupat and Ming-Wei Chang. It's a
 retrieval-augmented language model that firstly retrieves documents from a textual knowledge corpus and then
 utilizes retrieved documents to process question answering tasks.
 
@@ -34,8 +33,8 @@ explicit and implicit knowledge storage on three popular Open-QA benchmarks, and
 methods by a significant margin (4-16% absolute accuracy), while also providing qualitative benefits such as
 interpretability and modularity.*
 
-This model was contributed by `qqaatw <https://huggingface.co/qqaatw>`__. The original code can be found `here
-<https://github.com/google-research/language/tree/master/language/realm>`__.
+This model was contributed by [qqaatw](https://huggingface.co/qqaatw). The original code can be found
+[here](https://github.com/google-research/language/tree/master/language/realm).
 
 ## RealmConfig