Fixed command for translations extractor: (#2392)

Author: juskora

docs/extending/extending_online_editor.md

@@ -363,8 +363,8 @@ Use the example below to add a class choice to the Paragraph element in the `adm
     For example:
 
     ``` bash
-    php ./bin/console translation:extract --enable-extractor=ez_online_editor_attributes
-        --dir=./templates --output-dir=./translations/ --output-format=yaml
+    php ./bin/console translation:extract --enable-extractor=ez_online_editor_attributes \
+    --dir=./templates --output-dir=./translations/ --output-format=yaml
     ```
 
 ### Use cases