Add missing m2e repository to P2 director

Otherwise the setup fails when selecting "Eclipse SDK" rather than "IDE
for Eclipse committers" in the Oomph dialog.

Author: ptziegler

setups/WindowBuilder.setup

@@ -97,6 +97,8 @@
           name="com.github.spotbugs.plugin.eclipse.feature.group"/>
       <repository
           url="https://download.eclipse.org/windowbuilder/updates/nightly/latest/"/>
+      <repository
+          url="https://download.eclipse.org/technology/m2e/releases/latest/"/>
       <repository
           url="https://spotbugs.github.io/eclipse-latest/"/>
       <description>Install the tools needed in the IDE to work with the source code for Window Builder</description>