[librsvg-oci-images] rustc: do not run apt-upgrade

[Jordan Petridis <jpetridis src gnome org>]

commit 5a597265d017ee236e3057165f59b244303f919c
Author: Jordan Petridis <jpetridis gnome org>
Date:   Thu Oct 11 19:19:16 2018 +0300

    rustc: do not run apt-upgrade

 rustc/rustc_template | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/rustc/rustc_template b/rustc/rustc_template
index 4895474..f4bda38 100644
--- a/rustc/rustc_template
+++ b/rustc/rustc_template
@@ -1,7 +1,7 @@
 FROM debian:testing-slim
 
 # Librsvg deps
-RUN apt update -yqq && apt upgrade -yqq && \
+RUN apt update -yqq && \
     apt install -yqq --no-install-recommends \
     gcc make curl \
     automake autoconf libtool gettext itstool \