build

Bump Flask to 3.1.3 in acceptance test fixtures #23832

Job	Run time
testmask	1m 8s
cleanups	3s
validate-python-codegen	18s
validate-generated-is-up-to-date	1m 10s
integration-trigger	9s
make test (linux, direct)	5m 55s
make test (windows, direct)	9m 35s
make test (macos, terraform)	10m 44s
make test (windows, terraform)	16m 7s
make test (linux, terraform)	10m 10s
make test (macos, direct)	8m 40s
make test-pipelines	-1s
make test-exp-aitools	-1s
make test-exp-ssh	-1s
test-result	3s
	1h 3m 59s

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