fix(CI); autolabel correct json fields (leanprover-community#25661)

Apply the correct quotations to the json fields.

Author: adomani

.github/workflows/add_label_from_diff.yaml

@@ -41,12 +41,16 @@ jobs:
           printf 'Applying label %s\n' "${label}"
           # we use curl rather than octokit/request-action so that the job won't fail
           # (and send an annoying email) if the labels don't exist
+          url="https://api.github.com/repos/${{ github.repository }}/issues/${{ github.event.pull_request.number }}/labels"
+          printf 'url: %s\n' "${url}"
+          jsonLabel="$(printf '{"labels":["%s"]}' "${label}")"
+          printf 'jsonLabel: %s\n' "${jsonLabel}"
           curl --request POST \
             --header 'Accept: application/vnd.github+json' \
             --header 'authorization: Bearer ${{ secrets.GITHUB_TOKEN }}' \
             --header 'X-GitHub-Api-Version: 2022-11-28' \
-            --url https://api.github.com/repos/${{ github.repository }}/issues/${{ github.event.pull_request.number }}/labels \
-            --data "{'labels':[${label}]}"
+            --url "${url}" \
+            --data "${jsonLabel}"
         else
           echo "There is no single label that we could apply, so we are not applying any label."
         fi