Remove the deprecated RFC7523OAuthClientProvider #3637

Job	Run time
checks / pre-commit	57s
checks / docs	1m 4s
checks / test (3.10, lowest-direct, windows-latest)	1m 58s
checks / test (3.10, lowest-direct, ubuntu-latest)	1m 23s
checks / test (3.10, locked, ubuntu-latest)	1m 33s
checks / test (3.11, locked, windows-latest)	2m 3s
checks / test (3.14, lowest-direct, windows-latest)	1m 56s
checks / test (3.11, lowest-direct, windows-latest)	1m 51s
checks / readme-snippets	12s
checks / test (3.14, locked, windows-latest)	1m 58s
checks / test (3.10, locked, windows-latest)	2m 13s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 20s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 14s
checks / test (3.11, locked, ubuntu-latest)	1m 0s
checks / test (3.13, locked, ubuntu-latest)	1m 17s
checks / test (3.11, lowest-direct, ubuntu-latest)	1m 27s
checks / test (3.12, locked, ubuntu-latest)	1m 41s
checks / test (3.12, locked, windows-latest)	1m 56s
checks / test (3.13, lowest-direct, windows-latest)	1m 56s
checks / test (3.13, locked, windows-latest)	2m 3s
checks / test (3.12, lowest-direct, windows-latest)	2m 5s
checks / test (3.14, locked, ubuntu-latest)	1m 17s
checks / test (3.13, lowest-direct, ubuntu-latest)	1m 23s
all-green	2s
	35m 49s

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