Re-enable Linux CI (#73)

* Re-enable tests on Linux

* Use ubuntu-latest

* Update Swift setup action in GitHub workflow

Author: mikeger

.github/workflows/test.yml

@@ -17,11 +17,10 @@ jobs:
       run: swift test -v
 
   test-linux:
-    if: false
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v3
-    - uses: swift-actions/setup-swift@v2
+    - uses: SwiftyLab/setup-swift@latest
       with:
         swift-version: "6.1.0"
     - name: Get swift version