RFR [9] 8040147: tidy warnings cleanup for javax.transaction

[alexander stepanov]

Hello,

Could you please review the fix
http://cr.openjdk.java.net/~avstepan/8040147/webrev.01/
for
https://bugs.openjdk.java.net/browse/JDK-8040147

Just a very minor fix of docs markup.

Thanks,
Alexander