[docs] Changed csv lexer to text in import-export.rst

Author: nemesifier

docs/user/import-export.rst

@@ -16,7 +16,7 @@ needed, for example, the following CSV file will import a device named
 ``TestImport`` with mac address ``00:11:22:09:44:55`` in the organization
 with UUID ``3cb5e18c-0312-48ab-8dbd-038b8415bd6f``:
 
-.. code-block:: csv
+.. code-block:: text
 
     organization,name,mac_address
     3cb5e18c-0312-48ab-8dbd-038b8415bd6f,TestImport,00:11:22:09:44:55