Remove translations encoding workaround for Java 8

To work around translations visual corruption Res.java has been modified:

This should be reverted back after Spark is moved to Java 11 or newer

 Changes were applied to:

/src/main/java/org/jivesoftware/resource/Res.java
/plugins/flashing/src/main/java/org/jivesoftware/spark/plugin/flashing/FlashingResources.java
/plugins/roar/src/main/java/org/jivesoftware/spark/roar/RoarResources.java
/plugins/transferguard/src/main/java/org/jivesoftware/spark/plugins/transfersettings/TGuardRes.java
/plugins/fastpath/src/main/java/org/jivesoftware/fastpath/FpRes.java

Another change to Res.java to fix idle message and typing notifications https://github.com/igniterealtime/Spark/commit/1ee8fda88e5190350ca6d79a65aba0668ee532d0

Other plugins possibly are also affected, but they are either not active, not working in 2.9.0 or doesn't have UI. Same fix should be applied if required (maybe to Battleships, Reversi, TicTacToe, Spelling, OTR, etc.)