Update common github actions (#439)

Signed-off-by: Knative Automation <automation@knative.team>

.github/workflows/knative-security.yaml

@@ -37,11 +37,6 @@ jobs:
         # a pull request then we can checkout the head.
         fetch-depth: 2
 
-    # If this run was triggered by a pull request event, then checkout
-    # the head of the pull request instead of the merge commit.
-    - run: git checkout HEAD^2
-      if: ${{ github.event_name == 'pull_request' }}
-
     # Initializes the CodeQL tools for scanning.
     - name: Initialize CodeQL
       uses: github/codeql-action/init@v1

.github/workflows/knative-style.yaml

@@ -147,7 +147,7 @@ jobs:
           git check-attr --stdin linguist-generated | grep -Ev ': (set|true)$' | cut -d: -f1 |
           git check-attr --stdin linguist-vendored | grep -Ev ': (set|true)$' | cut -d: -f1 |
           grep -Ev '^(vendor/|third_party/|.git)' |
-          xargs misspell -error |
+          xargs misspell -i importas -error |
           reviewdog -efm="%f:%l:%c: %m" \
                 -name="github.com/client9/misspell" \
                 -reporter="github-pr-check" \