Remove the deprecated RFC7523OAuthClientProvider #3644

Job	Run time
checks / pre-commit	53s
checks / docs	1m 7s
checks / readme-snippets	15s
checks / test (3.11, lowest-direct, ubuntu-latest)	1m 23s
checks / test (3.10, lowest-direct, windows-latest)	1m 57s
checks / test (3.11, locked, windows-latest)	1m 55s
checks / test (3.10, lowest-direct, ubuntu-latest)	1m 25s
checks / test (3.10, locked, windows-latest)	2m 31s
checks / test (3.10, locked, ubuntu-latest)	1m 37s
checks / test (3.13, lowest-direct, windows-latest)	2m 12s
checks / test (3.13, locked, windows-latest)	1m 51s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 20s
checks / test (3.13, locked, ubuntu-latest)	1m 19s
checks / test (3.12, lowest-direct, windows-latest)	2m 0s
checks / test (3.12, locked, windows-latest)	1m 51s
checks / test (3.13, lowest-direct, ubuntu-latest)	1m 20s
checks / test (3.11, lowest-direct, windows-latest)	2m 1s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 28s
checks / test (3.12, locked, ubuntu-latest)	1m 37s
checks / test (3.14, lowest-direct, windows-latest)	1m 57s
checks / test (3.11, locked, ubuntu-latest)	1m 6s
checks / test (3.14, locked, windows-latest)	2m 2s
checks / test (3.14, locked, ubuntu-latest)	1m 16s
all-green	5s
	36m 28s

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