No longer hide nested projects

Change the Oomph setup to no longer hide nested Maven projects
so that https://bugs.eclipse.org/bugs/show_bug.cgi?id=553789
doesn't get triggered.

See gh-19280

eclipse/spring-boot-project.setup

@@ -223,7 +223,7 @@
     <setupTask
         xsi:type="setup:PreferenceTask"
         key="/instance/org.eclipse.m2e.core/eclipse.m2.hideFoldersOfNestedProjects"
-        value="true"/>
+        value="false"/>
     <setupTask
         xsi:type="setup:PreferenceTask"
         key="/instance/org.eclipse.m2e.core/eclipse.m2.updateIndexes"