Use final release URL of Eclipse Platform

Change-Id: I5f9562be8a16de07fa35ae78fb9560c14bf02db7
Signed-off-by: Markus Knauer <mknauer@eclipsesource.com>
diff --git a/releng/org.eclipse.rap.build/pom.xml b/releng/org.eclipse.rap.build/pom.xml
index 9a667e8..fb344a0 100644
--- a/releng/org.eclipse.rap.build/pom.xml
+++ b/releng/org.eclipse.rap.build/pom.xml
@@ -29,7 +29,7 @@
      -->
     <jetty-repo.url>https://download.eclipse.org/webtools/jetty/10.0.5/repository/</jetty-repo.url>
     <orbit-repo.url>https://download.eclipse.org/tools/orbit/downloads/2021-06/</orbit-repo.url>
-    <platform-repo.url>https://download.eclipse.org/eclipse/updates/4.20-I-builds/I20210611-1600/</platform-repo.url>
+    <platform-repo.url>https://download.eclipse.org/eclipse/updates/4.20/R-4.20-202106111600/</platform-repo.url>
     <rap-extra-repo.url>https://download.eclipse.org/rt/rap/base-platforms/3.14/extra-dependencies/</rap-extra-repo.url>
     <license-repo.url>https://download.eclipse.org/cbi/updates/license/</license-repo.url>
     <!-- The build type, N for nighty builds, S for stable builds. S-builds will be signed. -->