Update flat.yaml

.github/workflows/flat.yaml

@@ -21,7 +21,7 @@ jobs:
         with:
           deno-version: v1.x
       - name: Print Message
-        run: echo "https://kalshi-public-docs.s3.amazonaws.com/reporting/market_data_$(date +'%Y-%m-%d').json"
+        run: echo "https://kalshi-public-docs.s3.amazonaws.com/reporting/market_data_$(date -d "1 day ago" +'%Y-%m-%d').json"
       # The third step is a Flat Action step. We fetch the data in the http_url and save it as downloaded_filename
       - name: Fetch data 
         uses: githubocto/flat@v3