fix: invalid API url

I misstyped the API URL T-T

retrieve-old-report.sh

@@ -5,7 +5,7 @@
 repo_info() {
   curl -X GET \
     -H "Authorization: token $GITHUB_TOKEN" \
-    -H 'accept: application/json' \
+    -H 'Accept: application/json' \
     "$GITHUB_API_URL/repos/$GITHUB_REPOSITORY"
 }
 
@@ -22,7 +22,7 @@ base_report_url() {
   curl -X 'GET' \
     "$GITHUB_API_URL/repos/$GITHUB_REPOSITORY/actions/tasks" \
     -H "Authorization: token $GITHUB_TOKEN" \
-    -H 'accept: application/json' |
+    -H 'Accept: application/json' |
     jq --raw-output \
       --arg name "$JOB_NAME" \
       --arg head_branch "$1" \