Restrict httpx version to <1.0.0 #1638

Job	Run time
checks / pre-commit	38s
checks / readme-snippets	11s
checks / test (3.11, lowest-direct, windows-latest)	2m 43s
checks / test (3.11, lowest-direct, ubuntu-latest)	56s
checks / test (3.11, locked, ubuntu-latest)	51s
checks / test (3.12, locked, windows-latest)	3m 41s
checks / test (3.11, locked, windows-latest)	3m 7s
checks / test (3.10, locked, ubuntu-latest)	50s
checks / test (3.10, lowest-direct, ubuntu-latest)	50s
checks / test (3.12, locked, ubuntu-latest)	54s
checks / test (3.10, lowest-direct, windows-latest)	2m 21s
checks / test (3.12, lowest-direct, windows-latest)	4m 7s
checks / test (3.13, lowest-direct, ubuntu-latest)	54s
checks / test (3.13, locked, ubuntu-latest)	48s
checks / test (3.14, lowest-direct, windows-latest)	2m 12s
checks / test (3.12, lowest-direct, ubuntu-latest)	54s
checks / test (3.10, locked, windows-latest)	2m 12s
checks / test (3.14, locked, windows-latest)	3m 14s
checks / test (3.14, locked, ubuntu-latest)	2m 12s
checks / test (3.13, locked, windows-latest)	2m 10s
checks / test (3.13, lowest-direct, windows-latest)	2m 39s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 10s
all-green	3s
	39m 37s

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