Dockerfile: drop quiet option

Dockerfile

@@ -4,7 +4,7 @@ FROM gentoo/stage3:latest
 COPY --from=portage /var/db/repos/gentoo /var/db/repos/gentoo
 
 ENV ACCEPT_KEYWORDS="~amd64" \
-    EMERGE_DEFAULT_OPTS="--jobs=4 --quiet" \
+    EMERGE_DEFAULT_OPTS="--jobs=4" \
     FEATURES="-sandbox -usersandbox -ipc-sandbox -mount-sandbox -network-sandbox -pid-sandbox" \
     MAKEOPTS="-j4" \
     USE="-perl"