Run apibuild using 2021-09 not oxygen!

Change-Id: Iea9497c5d7e3521a7564006b58f734c6a3c3c0fb
Signed-off-by: Alexander Kurtakov <akurtako@redhat.com>
Reviewed-on: https://git.eclipse.org/r/c/linuxtools/org.eclipse.linuxtools/+/187502
Tested-by: Linux Tools Bot <linuxtools-bot@eclipse.org>

pom.xml

diff --git a/pom.xml b/pom.xml
index 034b353..eedb2fe 100644
--- a/pom.xml
+++ b/pom.xml
@@ -152,7 +152,7 @@
                 <repository>
                   <id>eclipse</id>
                   <layout>p2</layout>
-                  <url>http://download.eclipse.org/releases/oxygen</url>
+                  <url>http://download.eclipse.org/releases/2021-09</url>
                 </repository>
               </repositories>
               <!-- actuall indexer call -->