Translations from transifex, fix some strings references

OpenKeychain/src/main/res/raw-pl/help_changelog.html

@@ -1,6 +1,13 @@
 <html>
 <head></head>
 <body>
+<h2>2.6</h2>
+<ul>
+<li>key certifications (thanks to Vincent Breitmoser)</li>
+<li>new design for signature verification</li>
+<li>custom key length (thanks to Greg Witczak)</li>
+<li>fix share-functionality from other apps</li>
+</ul>
 <h2>2.5</h2>
 <ul>
 <li>naprawiono deszyfrowanie symetrycznych wiadomości/plików PGP</li>