Doc: do not claim that SUBDIRS.depends is only available for Makefiles

This information is outdated.

Change-Id: Ic2e10f7c858eed6f1b7c550995cb29004b4bd280
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>

qmake/doc/src/qmake-manual.qdoc

@@ -2408,7 +2408,6 @@
     \row \li .file       \li Specify the subproject \c pro file explicitly. Cannot be
                         used in conjunction with \c .subdir modifier.
     \row \li .depends    \li This subproject depends on specified subproject.
-                        Available only on platforms that use makefiles.
     \row \li .makefile   \li The makefile of subproject.
                         Available only on platforms that use makefiles.
     \row \li .target     \li Base string used for makefile targets related to this