[doc] Simplify README, incl. remove duplicates after hotfix #4351

Job	Run time
pre-commit / pre-commit	1m 15s
ubuntu / clang-build (ubuntu-24.04)	2m 52s
ubuntu / clang-build (ubuntu-24.04-arm)	2m 47s
mac / clang-build (Release)	1m 56s
windows / msvc-build (Release)	1m 56s
windows / msvc-build (Debug)	3m 33s
mac / clang-build (Debug)	2m 14s
windows / clang-build	3m 48s
ubuntu / gcc-build (ubuntu-24.04, Release)	2m 21s
ubuntu / gcc-build (ubuntu-24.04-arm, Debug)	2m 22s
ubuntu / gcc-build (ubuntu-24.04, Debug)	2m 40s
ubuntu / gcc-build (ubuntu-24.04-arm, Release)	2m 6s
mac / clang-test	4m 42s
ubuntu / clang-test (ubuntu-24.04-arm)	8m 22s
ubuntu / clang-test (ubuntu-24.04)	8m 28s
ubuntu / clang-sanitizer-build (ubuntu-24.04)	3m 0s
windows / msvc-test	5m 1s
ubuntu / gcc-test (ubuntu-24.04)	8m 22s
ubuntu / gcc-test (ubuntu-24.04-arm)	8m 21s
windows / clang-test	2m 58s
mac / clang-test-extended	2m 53s
windows / msvc-test-extended	2m 53s
ubuntu / clang-sanitizer-test (ubuntu-24.04)	2m 56s
windows / clang-test-extended	3m 48s
ubuntu / clang-test-extended (ubuntu-24.04)	4m 35s
ubuntu / clang-test-extended (ubuntu-24.04-arm)	4m 32s
ubuntu / gcc-test-extended (ubuntu-24.04)	4m 33s
ubuntu / gcc-test-extended (ubuntu-24.04-arm)	4m 27s
ubuntu / clang-sanitizer-test-extended (ubuntu-24.04)	2m 31s
ubuntu / gcc-build-codecov	7m 21s
perf / ubuntu-gcc-build-perf-stats	2m 27s
perf / macos-clang-build-perf-stats	1m 36s
pages / build-doxygen-xml	23s
pages / build-scoreboard	20s
pages / build-sphinx	42s
pages / deploy-pages	0s
	2h 5m 1s

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