patch 8.2.1487: Travis: installing snd-dummy is not always useful

Problem:    Travis: installing snd-dummy is not always useful.
Solution:   Only install snd-dummy on amd64. (Ozaki Kiichi, closes #6738)
diff --git a/ci/load-snd-dummy.sh b/ci/load-snd-dummy.sh
index 5ceb7ce..b0101b0 100644
--- a/ci/load-snd-dummy.sh
+++ b/ci/load-snd-dummy.sh
@@ -3,6 +3,6 @@
 
 if ! modprobe snd-dummy; then
     # snd-dummy is contained in linux-modules-extra (if exists)
-    apt install -y "linux-modules-extra-$(uname -r)"
+    apt-get install -yq --no-install-suggests --no-install-recommends "linux-modules-extra-$(uname -r)"
     modprobe snd-dummy
 fi