Drop deprecated `streamablehttp_client` #4012

Job	Run time
checks / pre-commit	38s
checks / readme-snippets	11s
checks / test (3.12, highest, ubuntu-latest)	53s
checks / test (3.11, highest, windows-latest)	2m 27s
checks / test (3.12, lowest-direct, ubuntu-latest)	48s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 10s
checks / test (3.13, lowest-direct, ubuntu-latest)	46s
checks / test (3.13, lowest-direct, windows-latest)	2m 42s
checks / test (3.10, highest, windows-latest)	2m 16s
checks / test (3.11, lowest-direct, windows-latest)	2m 34s
checks / test (3.14, lowest-direct, windows-latest)	2m 11s
checks / test (3.11, lowest-direct, ubuntu-latest)	44s
checks / test (3.10, lowest-direct, ubuntu-latest)	48s
checks / test (3.12, highest, windows-latest)	3m 27s
checks / test (3.13, highest, ubuntu-latest)	45s
checks / test (3.10, lowest-direct, windows-latest)	2m 17s
checks / test (3.10, highest, ubuntu-latest)	48s
checks / test (3.11, highest, ubuntu-latest)	46s
checks / test (3.12, lowest-direct, windows-latest)	3m 21s
checks / test (3.14, highest, windows-latest)	2m 32s
checks / test (3.14, highest, ubuntu-latest)	1m 13s
checks / test (3.13, highest, windows-latest)	2m 23s
	35m 40s

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