changelog 5.3

OpenKeychain/src/main/res/raw/help_changelog.md

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 [//]: # (NOTE: Please put every sentence in its own line, Transifex puts every line in its own translation field!)
 
+## 5.3
+  * Usw keys.openpgp.org as default keyserver
+
 ## 5.2
   * Improved key import from clipboard