remove Java nature from org.eclipse.mylyn.help.ui

This was added in fab7fc72649fc9b970b6c73ef98aa922e73286b4 when the
implementation of the UI legened was initially put in the help bundle,
but now that there is no Java code in the help bundle, I can't
see any need for it, and it unnecessarily prevents consumers from
running the Eclipse info center with older Java versions.

Change-Id: I9deee44893243ce0da5825bb20310eab2c19e37c
3 files changed