README: don't depend on specific versions of Staticcheck or the action

We grow tired of having to update the README all the time, so just
depend on the latest versions. Users who actually care about proper
version management will do the right thing and pin to specific versions.

Closes: gh-12

README.md

@@ -19,9 +19,9 @@ jobs:
     - uses: actions/checkout@v2
       with:
         fetch-depth: 1
-    - uses: dominikh/staticcheck-action@v1.3.0
+    - uses: dominikh/staticcheck-action@v1
       with:
-        version: "2022.1.3"
+        version: "latest"
 ```
 
 A more advanced example that runs tests, go vet and Staticcheck on multiple OSs and Go versions looks like this:
@@ -49,9 +49,9 @@ jobs:
         go-version: ${{ matrix.go }}
     - run: "go test ./..."
     - run: "go vet ./..."
-    - uses: dominikh/staticcheck-action@v1.3.0
+    - uses: dominikh/staticcheck-action@v1
       with:
-        version: "2022.1.3"
+        version: "latest"
         install-go: false
         cache-key: ${{ matrix.go }}
         working-directory: ${{ matrix.dir }}