[gbm-web] Install ca-certificates explicitly

[Bartłomiej Piotrowski <bpiotrowski src gnome org>]

commit 8b506a3336444acc68a688ae75b1231f74eb7171
Author: Bartłomiej Piotrowski <bpiotrowski gnome org>
Date:   Thu Aug 27 15:54:04 2020 +0200

    Install ca-certificates explicitly

 flat-manager/Dockerfile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/flat-manager/Dockerfile b/flat-manager/Dockerfile
index 0926cd0..3be898d 100644
--- a/flat-manager/Dockerfile
+++ b/flat-manager/Dockerfile
@@ -3,7 +3,7 @@ FROM ubuntu:18.04
 RUN apt-get update && apt-get install -y gnupg2
 ADD ppa_alexlarsson_flatpak_bionic.list /etc/apt/sources.list.d/
 RUN apt-key adv --keyserver keyserver.ubuntu.com --recv-keys C793BFA2FA577F07 && \
-    apt-get update && apt-get install -y flatpak ostree libpq5 && \
+    apt-get update && apt-get install -y flatpak ostree libpq5 ca-certificates && \
     rm -rf /var/lib/apt/lists/*
 
 ADD flat-manager /usr/local/bin/flat-manager