Revert "Another experiment for memory leaks: Create a brand-new buffer for passthrough uncompressed content"

This reverts commit 92571a65db.

It looks like c3fab89bd7 nabbed it at last.

proxy/src/main/java/com/velocitypowered/proxy/protocol/netty/MinecraftCompressDecoder.java

@@ -29,8 +29,7 @@ public class MinecraftCompressDecoder extends MessageToMessageDecoder<ByteBuf> {
     int claimedUncompressedSize = ProtocolUtils.readVarInt(in);
     if (claimedUncompressedSize == 0) {
       // Strip the now-useless uncompressed size, this message is already uncompressed.
-      out.add(in.copy());
-      in.skipBytes(in.readableBytes());
+      out.add(in.retainedSlice());
       return;
     }