tests: docker: Increase VM building memory size to 1024MiB.

This fixes the following error when running the "docker-system" test:

In ice-9/ftw.scm:
   553:30  1 (_ #<directory stream db6660>)
In unknown file:
           0 (readdir #<directory stream db6660>)

ERROR: In procedure readdir:
In procedure readdir: Cannot allocate memory

* gnu/tests/docker.scm (%test-docker-system): Bump image building VM memory
size to 1024 MiB.

1 files changed, 2 insertions, 1 deletions

diff --git a/gnu/tests/docker.scm b/gnu/tests/docker.scm
index cbb856b016a..92611b0a8db 100644
--- a/gnu/tests/docker.scm
+++ b/gnu/tests/docker.scm
@@ -303,5 +303,6 @@ docker-image} inside Docker.")
                                         (inherit (simple-operating-system))
                                         ;; Use locales for a single libc to
                                         ;; reduce space requirements.
-                                        (locale-libcs (list glibc))))
+                                        (locale-libcs (list glibc)))
+                                      #:memory-size 1024)
                  run-docker-system-test)))))