Remove remaining explicit source-features from eclipse-sdk target

Source features are not needed anymore at all (the TP is configured to
automatically include sources), now that the eclipse.sdk feature does
not include source features explicitly anymore:
- eclipse-platform#3100

Follow-up on
- eclipse-platform#2777

Author: HannesWell

eclipse.platform.releng.prereqs.sdk/eclipse-sdk-prereqs.target

@@ -39,29 +39,20 @@
     <location includeAllPlatforms="true" includeConfigurePhase="false" includeMode="slicer" includeSource="true" type="InstallableUnit">
        <!-- Check version in "<EMF>/features" directory -->
       <unit id="org.eclipse.emf.common.feature.group" version="2.35.0.v20250401-0947"/>
-      <unit id="org.eclipse.emf.common.source.feature.group" version="2.35.0.v20250401-0947"/>
       <unit id="org.eclipse.emf.ecore.feature.group" version="2.40.0.v20250414-1351"/>
-      <unit id="org.eclipse.emf.ecore.source.feature.group" version="2.40.0.v20250414-1351"/>
        <!-- For org.eclipse.ui.tools, and PDE's spy dependencies as of Eclipse 4.22 -->
        <!-- Check version in "<EMF>/features" directory -->
       <unit id="org.eclipse.emf.edit.feature.group" version="2.24.0.v20250330-0741"/>
-      <unit id="org.eclipse.emf.edit.source.feature.group" version="2.24.0.v20250330-0741"/>
       <unit id="org.eclipse.emf.databinding.feature.group" version="1.12.0.v20240604-0832"/>
-      <unit id="org.eclipse.emf.databinding.source.feature.group" version="1.12.0.v20240604-0832"/>
       <unit id="org.eclipse.emf.databinding.edit.feature.group" version="1.12.0.v20240604-0832"/>
-      <unit id="org.eclipse.emf.databinding.edit.source.feature.group" version="1.12.0.v20240604-0832"/>
       <repository location="https://download.eclipse.org/modeling/emf/emf/builds/release/2.42.0"/>
     </location>
 
     <location includeAllPlatforms="true" includeConfigurePhase="false" includeMode="slicer" includeSource="true" type="InstallableUnit">
       <unit id="org.eclipse.ecf.core.feature.feature.group" version="1.7.0.v20250304-2338"/>
-      <unit id="org.eclipse.ecf.core.feature.source.feature.group" version="1.7.0.v20250304-2338"/>
       <unit id="org.eclipse.ecf.filetransfer.feature.feature.group" version="3.15.0.v20250115-0406"/>
-      <unit id="org.eclipse.ecf.filetransfer.feature.source.feature.group" version="3.15.0.v20250115-0406"/>
       <unit id="org.eclipse.ecf.filetransfer.httpclientjava.feature.feature.group" version="2.1.0.v20250108-1923"/>
-      <unit id="org.eclipse.ecf.filetransfer.httpclientjava.feature.source.feature.group" version="2.1.0.v20250108-1923"/>
       <unit id="org.eclipse.ecf.filetransfer.httpclient5.feature.feature.group" version="1.2.0.v20250522-2300"/>
-      <unit id="org.eclipse.ecf.filetransfer.httpclient5.feature.source.feature.group" version="1.2.0.v20250522-2300"/>
       <repository location="https://download.eclipse.org/rt/ecf/3.16.2/site.p2/3.16.2.v20250528-1917"/>
     </location>