Revert "Update `shell.nix` to `nixpkgs-24.05` and LLVM 18 (#14651)" #12881

Job	Run time
check_format	1m 37s
x86_64-gnu-test (1.7.3)	36m 38s
x86_64-gnu-test (1.8.2)	36m 7s
x86_64-gnu-test (1.9.2)	35m 41s
x86_64-gnu-test (1.10.1)	37m 3s
x86_64-gnu-test (1.11.2)	34m 7s
x86_64-gnu-test (1.12.2)	35m 51s
x86_64-gnu-test (1.13.3)	35m 19s
x86_64-gnu-test (1.14.0)	36m 3s
x86_64-gnu-test-preview_mt	5m 43s
x86_64-gnu-test (1.0.0, FLAGS=-Dwithout_ffi USE_PCRE1=true)	33m 21s
x86_64-gnu-test (1.1.1, FLAGS=-Dwithout_ffi USE_PCRE1=true)	34m 44s
x86_64-musl-test	43m 10s
x86_64-gnu-test (1.2.2, USE_PCRE1=true)	35m 10s
x86_64-gnu-test (1.3.2, USE_PCRE1=true)	35m 20s
x86_64-gnu-test (1.4.1, USE_PCRE1=true)	37m 30s
x86_64-gnu-test (1.5.1, USE_PCRE1=true)	34m 40s
x86_64-gnu-test (1.6.2, USE_PCRE1=true)	33m 37s
	9h 41m 41s

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