[fix] strings containing HTML code are not saved

## Reproduce the issue

Edit a translation with standard editor (clicking on the name). Modify any string to add HTML code inside. Example: "My language string for <strong>Jean-Marie</strong>" (note the strong tags)

## Expected result

HTML is saved

## Result

HTML is cleared because the way that $_POST data is received by the model

## Patch test

Apply the patch and check it. HTML should be saved correctly.