Merge pull request DSpace#4219 from michdyk/patch-2

Full update pl translations and minor changes in cz and uk translations

Author: tdonohue

src/assets/i18n/cs.json5

@@ -9221,7 +9221,7 @@
   "thumbnail.default.alt": "Náhled",
 
   // "thumbnail.default.placeholder": "No Thumbnail Available",
-  "thumbnail.default.placeholder": "Náhled není k dispozici",
+  "thumbnail.default.placeholder": "Miniatura neexistuje",
 
   // "thumbnail.project.alt": "Project Logo",
   "thumbnail.project.alt": "Logo projektu",
@@ -11690,4 +11690,4 @@
   "embargo.listelement.badge": "Embargo until {{ date }}",
 
 
-}
+}