Upgrade Pex PEX scies to Python 3.13. #3223

Job	Run time
Check GitHub Organization	1s
tox -e py313-pip24_3_1	19m 10s
./dtox.sh -e py27-pip20	10m 19s
tox -e py313-pip24_3_1-integration --shard 1/2	25m 10s
tox -e format-check,lint-check,typecheck,enum-check,vendor-check,package,docs	10m 37s
./dtox.sh -e py38-pip22_3_1	17m 46s
tox -e py313-pip24_3_1-integration --shard 2/2	25m 20s
./dtox.sh -e py311-pip23_3_2	18m 15s
./dtox.sh -e py313-pip24_3_1	14m 21s
./dtox.sh -e py314-pip24_3_1	15m 21s
./dtox.sh -e pypy310-pip24_3_1	28m 9s
./dtox.sh -e py27-pip20-integration	28m 27s
./dtox.sh -e py38-pip22_3_1-integration --shard 1/2	33m 38s
./dtox.sh -e py38-pip22_3_1-integration --shard 2/2	28m 45s
./dtox.sh -e py311-pip23_3_2-integration --shard 1/2	29m 4s
./dtox.sh -e py311-pip23_3_2-integration --shard 2/2	30m 25s
./dtox.sh -e py313-pip24_3_1-integration --shard 1/2	26m 27s
./dtox.sh -e py313-pip24_3_1-integration --shard 2/2	27m 29s
./dtox.sh -e py314-pip24_3_1-integration --shard 1/2	26m 12s
./dtox.sh -e py314-pip24_3_1-integration --shard 2/2	28m 43s
./dtox.sh -e pypy310-pip24_3_1-integration --shard 1/2	47m 19s
./dtox.sh -e pypy310-pip24_3_1-integration --shard 2/2	50m 3s
Gather Final Status	1s
	9h 1m 2s

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