github-workflows: remove redundant pdftexcmds installation on mac

Change-Id: Ied981b7ae9ef8842e31e6978922213f11d59270a
diff --git a/.github/workflows/check-mac.yaml b/.github/workflows/check-mac.yaml
index 8ff8cb6..44f57d0 100644
--- a/.github/workflows/check-mac.yaml
+++ b/.github/workflows/check-mac.yaml
@@ -30,11 +30,6 @@
       - uses: r-lib/actions/setup-tinytex@master
         if: contains(matrix.config.args, 'no-manual') == false
 
-      - name: Install system dependencies
-        if: runner.os == 'macOS'
-        run: |
-          tlmgr install pdftexcmds
-
       - name: Cache R packages
         uses: actions/cache@v1
         with: