Update messages_pl.properties

Changelog:
---
* Added:
kitError2 (216)
kitNotFound (536)
socialSpy (537)
setBal (538)
insufficientFunds (540)

* Fixed:
backUsageMsg (21)
banFormat (28)
bedMissing (30)
connectedPlayers (58)
downloadingGeoIp (91)
fullStack (125)
geoIpUrlEmpty (131)
geoIpUrlInvalid (132)
healOther (148)
itemSpawn (200)
jailReleased (206)
jailSentenceExtended (208)
jailSet (209)
kickedAll (213)
kitInvFull (221)
kitOnce (222)
markMailAsRead (239)
matchingIPAddress (242)
messageTruncated (246)
nickChanged (272)
removed (376)
repairNone (381)
teleportAll (419)
tempBanned (434)
thunderDuration (437)
timeSet (442)
totalWorthAll (446)
totalWorthBlocks (447)
tradeSignEmpty (450)
youAreHealed (520)
youHaveNewMail (521)
balanceOther (527)
Merge pull request #465 from skmedix/patch-1

Update Polish translation