Update Tycho pomless to 2.6.0

Change-Id: If513e31c555cce54f018ee1a3c0171e2afbcc129
Reviewed-on: https://git.eclipse.org/r/c/platform/eclipse.platform.runtime/+/189875
Tested-by: Platform Bot <platform-bot@eclipse.org>
Reviewed-by: Alexander Kurtakov <akurtako@redhat.com>

.mvn/extensions.xml

diff --git a/.mvn/extensions.xml b/.mvn/extensions.xml
index f998810..5125b72 100644
--- a/.mvn/extensions.xml
+++ b/.mvn/extensions.xml
@@ -3,6 +3,6 @@
   <extension>
     <groupId>org.eclipse.tycho.extras</groupId>
     <artifactId>tycho-pomless</artifactId>
-    <version>2.5.0</version>
+    <version>2.6.0</version>
   </extension>
 </extensions>
\ No newline at end of file