[BUGFIX] Use correct namespace in ext_emconf.php

`ext_emconf.php` contains the php autoloading definition
for class mode instances which should be obsolete nower
days but kept until final investigated.

Due to `copy&pasta` error when creating this extension,
the wrong namespace has been left in `ext_emconf.php`,
which is now corrected.

Author: sbuerk

ext_emconf.php

@@ -23,7 +23,7 @@
     ],
     'autoload' => [
         'psr-4' => [
-            'WebVision\\Deepltranslate\\Core\\' => 'Classes',
+            'WebVision\\Deepl\\Base\\' => 'Classes',
         ],
     ],
 ];