fix(plugin-multi-tenant): improve translation for "Tenant" (use "Mandant" instead of "Mieter") (#15537)

Currently, the term "Tenant" is translated as "Mieter" in German. While
"Mieter" is a literal translation (meaning a person who rents an
apartment), the correct technical term in a software/SaaS context for
multi-tenancy is "Mandant".

This PR updates the German localization to use the industry-standard
terminology to avoid confusion for German-speaking users.

Author: blankse

packages/plugin-multi-tenant/src/translations/languages/de.ts

@@ -2,10 +2,10 @@ import type { PluginDefaultTranslationsObject, PluginLanguage } from '../types.j
 
 export const deTranslations: PluginDefaultTranslationsObject = {
   'plugin-multi-tenant': {
-    'assign-tenant-button-label': 'Mieter zuweisen',
+    'assign-tenant-button-label': 'Mandant zuweisen',
     'assign-tenant-modal-title': 'Weisen Sie "{{title}}" zu',
     'field-assignedTenant-label': 'Zugewiesener Mandant',
-    'nav-tenantSelector-label': 'Mieter',
+    'nav-tenantSelector-label': 'Nach Mandanten filtern',
   },
 }