nixosTests.gitea,nixosTests.forgejo: fix test on `i686-linux`

Fail pattern:
1. Unsuspecting `qemu-kvm` notice:
```
server # qemu-kvm: at most 2047 MB RAM can be simulated
```

2. Hard fail
```
    self.shell.send(out_command.encode())
BrokenPipeError: [Errno 32] Broken pipe
```

(Took me a while to consider those lines are related)

1 files changed, 1 insertions, 1 deletions

diff --git a/nixos/tests/gitea.nix b/nixos/tests/gitea.nix
index c38aad1f44e..4e6f9c79a6f 100644
--- a/nixos/tests/gitea.nix
+++ b/nixos/tests/gitea.nix
@@ -30,7 +30,7 @@ let
 
     nodes = {
       server = { config, pkgs, ... }: {
-        virtualisation.memorySize = 2048;
+        virtualisation.memorySize = 2047;
         services.gitea = {
           enable = true;
           database = { inherit type; };