This is normal for a number of e4 APIs. These APIs have not yet been finalized so they are left 'discouraged' - but you have to use them for e4 applications. There is a chance that they may change in future Eclipse releases.
You can turn off the warning in Preferences > Java > Compiler > Errors/Warning
in the Deprecated and restricted API
section change Discouraged reference (access rules)
to ignore
. Or you can use @SuppressWarning("restriction")
on your class.
Eclipse bug 412373 will list the APIs which will finalized in Eclipse 4.4 (Luna), but currently it is empty. Some e4 APIs were finalized when 4.3 was released.