patch 9.0.1473: CI does not run sound tests

Problem:    CI does not run sound tests.
Solution:   Re-enable sound tests.  Use "apt-get" instead of "apt". (Ozaki
            Kiichi, closes #12280)
diff --git a/src/version.c b/src/version.c
index 611bd82..c3e2afe 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1473,
+/**/
     1472,
 /**/
     1471,