Fix tests failing to run on Mac

[fbricon]

Fixes this error:

[INFO] --- tycho-surefire:4.0.6:test (default-test) @ org.eclipse.jdt.ls.tests ---
[INFO] {osgi.os=macosx, [osgi.ws](http://osgi.ws/)=cocoa, org.eclipse.update.install.features=true, osgi.arch=x86_64, org.eclipse.update.install.sources=true}
[ERROR] Cannot resolve project dependencies:
[ERROR]   You requested to install ‘org.eclipse.equinox.p2.iu; org.eclipse.jdt.feature.group 0.0.0’ but it could not be found
[ERROR]
[ERROR] See https://wiki.eclipse.org/Tycho/Dependency_Resolution_Troubleshooting for help.

[rgrunber]

Good catch. It's a stale reference from after #2963 which removed the JDT feature group IU from the target.