[FIX] base_import: BS4, visible error text on import fail

In BS3, the combination "text-danger" and "bg-danger" worked as the red
color for texts was not the same as the red color for backgrounds. With
BS4, they are the same so it does not make sense.

Fortunately, we introduced a mixin customization which automatically
selects the correct color according to the background. So removing the
"text-danger" part is enough to make sure the text will be visible over
"bg-danger" background.

addons/base_import/static/src/xml/base_import.xml

@@ -121,7 +121,7 @@
         </tbody>
     </t>
     <t t-name="ImportView.preview.error">
-        <div class="oe_import_report bg-danger text-danger">
+        <div class="oe_import_report bg-danger">
             <p>Import preview failed due to: <t t-esc="error"/>.</p>
             <p>For CSV files, you may need to select the correct separator.</p>
             <p t-if="preview">Here is the start of the file we could not import:</p>