chore: Run CI on ubuntu-latest runner (#1949)

* Update test.yml

* remove single thread

* chore: remove `RUST_TEST_THREADS` from flake.nix

---------

Co-authored-by: TomAFrench <tom@tomfren.ch>

.github/workflows/test.yml

@@ -20,7 +20,7 @@ jobs:
       matrix:
         include:
           - os: ubuntu
-            runner: ubuntu-large
+            runner: ubuntu-latest
             target: x86_64-linux
 
     steps:

flake.nix

@@ -88,14 +88,7 @@
         BARRETENBERG_BIN_DIR = "${pkgs.barretenberg-wasm}/bin";
       };
 
-      testEnvironment = sharedEnvironment // {
-        # Barretenberg fails if tests are run on multiple threads, so we set the test thread
-        # count to 1 throughout the entire project
-        #
-        # Note: Setting this allows for consistent behavior across build and shells, but is mostly
-        # hidden from the developer - i.e. when they see the command being run via `nix flake check`
-        RUST_TEST_THREADS = "1";
-      };
+      testEnvironment = sharedEnvironment // {};
 
       # The `self.rev` property is only available when the working tree is not dirty
       GIT_COMMIT = if (self ? rev) then self.rev else "unknown";