depend on actions/checkout w/ a major version dep (#82)

diff --git a/.github/workflows/build.yaml b/.github/workflows/build.yaml
index b06adcc..a6d5ca6 100644
--- a/.github/workflows/build.yaml
+++ b/.github/workflows/build.yaml
@@ -11,7 +11,7 @@
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v3.0.0 
+    - uses: actions/checkout@v3
     - uses: dart-lang/setup-dart@v1.3
     - uses: nanasess/setup-chromedriver@v1.0.7