Small updates in polish translation

[Qrzysio]

Mostly grammar changes.

[darktrojan]

Hello, thanks for your pull request. I have some comments.

Firstly, the openwith.dtd and openwith.properties files are obsolete and days away from being removed. So I won't be taking those changes.

Secondly, don't turn … into .... The character exists for the purpose I'm using it for.

Also, I'm going to tag in the original author of this translation for their opinion, because I don't speak Polish. :-) @Matthaiks, what do you think of these changes?

[Qrzysio]

Thank you. In dtd and .properties files three dots ... have also been used. No problem to follow your rules anyway. Waiting for @Matthaiks then.

[Matthaiks]

I'm fine with those changes in the messages.json. I would move the comma placed after "darowizna" to after "najmniejsza" in _updatemessage, though.

[Qrzysio]

Dots are back + comma has been moved as Matthaiks suggested.