Update GitHub Actions workflows. (#394)

This PR was automatically generated by the
update-workflows-ecosystem-providers workflow in the pulumi/ci-mgmt
repo, from commit 765bc5726415923fbd41795fb83305b5044f722f.

.github/workflows/master.yml

@@ -174,7 +174,7 @@ jobs:
     - name: Echo Coverage Output Dir
       run: 'echo "Coverage output directory: ${{ env.COVERAGE_OUTPUT_DIR }}"'
     - name: Generate Coverage Data
-      run: make tfgen
+      run: PULUMI_MISSING_DOCS_ERROR=true make tfgen
     - name: Summarize Provider Coverage Results
       run: cat ${{ env.COVERAGE_OUTPUT_DIR }}/shortSummary.txt
     - name: Upload coverage data to S3