Bump tornado from 6.4.2 to 6.5.1 in /lambdas/preview (#4405)

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

lambdas/preview/requirements.txt

@@ -108,7 +108,7 @@ t4-lambda-shared[mem,preview] @ https://github.com/quiltdata/quilt/archive/d496d
     # via t4_lambda_preview (setup.py)
 tinycss2==1.4.0
     # via nbconvert
-tornado==6.4.2
+tornado==6.5.1
     # via jupyter-client
 traitlets==5.14.3
     # via