nixos/tests/rspamd: increase memory

rspamd seems to be consuming more memory now sometimes, causing OOMs in
the test.

Increase the memory given to these VMs to make the tests pass more
reliably.

nixos/tests/rspamd.nix

@@ -25,6 +25,7 @@ let
     machine = {
       services.rspamd.enable = true;
       networking.enableIPv6 = enableIPv6;
+      virtualisation.memorySize = 1024;
     };
     testScript = ''
       start_all()
@@ -68,6 +69,7 @@ in
           group = "rspamd";
         }];
       };
+      virtualisation.memorySize = 1024;
     };
 
     testScript = ''
@@ -116,6 +118,7 @@ in
           '';
         };
       };
+      virtualisation.memorySize = 1024;
     };
 
     testScript = ''
@@ -221,6 +224,7 @@ in
           rspamd_logger.infox(rspamd_config, 'Work dammit!!!')
         '';
       };
+      virtualisation.memorySize = 1024;
     };
     testScript = ''
       ${initMachine}
@@ -287,6 +291,7 @@ in
         postfix.enable = true;
         workers.rspamd_proxy.type = "rspamd_proxy";
       };
+      virtualisation.memorySize = 1024;
     };
     testScript = ''
       ${initMachine}