Replace dependency to org.eclipse.osgi.services

The bundle 'o.e.osgi.services' is deprecated for removal as part of
eclipse-equinox/equinox#18
and already has been changed to only re-export the 'official' OSGi
artifacts published to Maven-Central.

It should be replaced by imports of the desired org.osgi.service.*
packages so that the runtime can choose a suitable provider
independently of the bundle name.

org.eclipse.xtend.ide/META-INF/MANIFEST.MF

@@ -29,9 +29,9 @@ Require-Bundle: org.eclipse.xtend.core,
  org.eclipse.xtext.xbase.lib;bundle-version="2.34.0",
  org.eclipse.jdt.core.manipulation;bundle-version="1.16.0";resolution:=optional,
  org.eclipse.e4.core.services,
- org.eclipse.osgi.services,
  org.eclipse.e4.ui.css.swt.theme;bundle-version="0.13.0"
-Import-Package: org.apache.log4j;version="1.2.24"
+Import-Package: org.apache.log4j;version="1.2.24",
+ org.osgi.service.event;version="[1.4.0,2.0.0)"
 Bundle-RequiredExecutionEnvironment: JavaSE-11
 Bundle-Activator: org.eclipse.xtend.ide.XtendActivator
 Export-Package: org.eclipse.xtend.ide;x-internal:=true,