updated Polish translation

(cherry-picked from commit 65f690d905)

changelog.md

@@ -19,7 +19,7 @@
    * Fixed "Search" placeholder text in dialog item filters not being
      translatable (bug #2709, bug #2732).
    * Updated translations: British English, Chinese (Simplified), Czech, French,
-     Scottish Gaelic, Spanish, Ukrainian
+     Polish, Scottish Gaelic, Spanish, Ukrainian
  ### WML engine
    * Support formula= key in [variable] ConditionalWML
    * Support to_location in [move_unit], taking a location ID

players_changelog.md

@@ -5,7 +5,7 @@ changelog: https://github.com/wesnoth/wesnoth/blob/master/changelog.md
 ## Version 1.15.0-dev
  ### Language and i18n
    * Updated translations: British English, Chinese (Simplified), Czech, French,
-     Scottish Gaelic, Spanish, Ukrainian.
+     Polish, Scottish Gaelic, Spanish, Ukrainian.
  ### Miscellaneous and bug fixes
    * Fixed minimap buttons not doing anything (bug #2681)