Fix typos in mpt javadoc

[TianHengZhuang]

Fix minor typos in comments/javadoc/log messages. No functional change.

[chibenwa]

Thanks!

[TianHengZhuang]

Heads-up: both Jenkins pr-merge runs (#1, #2) failed in the james-server-protocols-imap4 module due to forked test JVM resource issues, not from this change:

• MPT-32 run external-james test when JAMES_ADDRESS env is set #1: There was a timeout in the fork (plus OutOfMemoryError: Java heap space earlier in the log)
• MPT-33 introduce namespace support feature and run related tests only… #2: OutOfMemoryError: Java heap space in surefire fork

This PR only touches javadoc in mpt/core (ProtocolSession.java, +3/-3) and is unrelated to the imap4 tests. The PR is already approved; could this be retriggered / merged? Thanks!

[Arsnael]

Rettriggered the build