Fix gifs

Gifs are not shown at https://teklia.gitlab.io/atr/dan/usage/predict/#description-of-parameters

docs/usage/predict.md

@@ -69,9 +69,8 @@ It will create the following JSON file named `dan_humu_page/predict/example.json
     "attention_gif": "dan_humu_page/predict/example_line.gif"
 }
 ```
-<video autoplay>
-    <source src="../assets/example_line.gif">
-</video>
+
+<img src="../../assets/example_line.gif" />
 
 ### Predict with confidence scores and word-level attention maps
 
@@ -100,6 +99,4 @@ It will create the following JSON file named `dan_humu_page/predict/example.json
     "attention_gif": "dan_humu_page/predict/example_word.gif"
 }
 ```
-<video autoplay>
-    <source src="../assets/example_word.gif">
-</video>
+<img src="../../assets/example_word.gif" >