Update jgit-4.18 target platform to use release repository

Change-Id: I62aaf1cb823e05f277b16b156d0f9a4928efe213

org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.18-staging.target → org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.18.target

 <?xml version="1.0" encoding="UTF-8" standalone="no"?>
 <?pde?>
 <!-- generated with https://github.com/eclipse-cbi/targetplatform-dsl -->
-<target name="jgit-4.18-staging" sequenceNumber="1606854603">
+<target name="jgit-4.18-staging" sequenceNumber="1608217757">
   <locations>
     <location includeMode="slicer" includeAllPlatforms="false" includeSource="true" includeConfigurePhase="true" type="InstallableUnit">
       <unit id="org.eclipse.jetty.client" version="9.4.30.v20200611"/>
     </location>
     <location includeMode="slicer" includeAllPlatforms="false" includeSource="true" includeConfigurePhase="true" type="InstallableUnit">
       <unit id="org.eclipse.osgi" version="0.0.0"/>
-      <repository location="https://download.eclipse.org/staging/2020-12/"/>
+      <repository location="https://download.eclipse.org/releases/2020-12/"/>
     </location>
   </locations>
 </target>

org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.18-staging.tpd → org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.18.tpd

 include "projects/jetty-9.4.x.tpd"
 include "orbit/R20201130205003-2020-12.tpd"
 
-location "https://download.eclipse.org/staging/2020-12/" {
+location "https://download.eclipse.org/releases/2020-12/" {
 	org.eclipse.osgi lazy
 }