build: Fix node version to 20.4 to work around issue with mock-fs

Author: TimothyJones

.github/workflows/ci.yaml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        node: [18, 20]
+        node: [18, 20.4]
         os: [ubuntu-latest, windows-latest]
     env:
         OS: ${{ matrix.os }}