Set version to 12.0.0-rc.6 (#8030) #8948

Job	Run time
build-compiler (ubuntu-24.04, ocaml-variants.4.14.2+options,ocaml-option-static, linux-x64, x86_6...	4m 39s
build-compiler (macos-15-intel, 5.3.0, true, darwin-x64, x86_64-apple-darwin)	14m 19s
build-compiler (ubuntu-24.04, ocaml-variants.5.3.0+options,ocaml-option-static, true, true, linux...	4m 58s
build-compiler (windows-2025, 5.3.0, true, win32-x64, x86_64-pc-windows-gnu, .exe)	9m 41s
build-compiler (ubuntu-24.04-arm, ocaml-variants.5.3.0+options,ocaml-option-static, true, true, t...	6m 10s
build-compiler (macos-15, 5.3.0, true, darwin-arm64, aarch64-apple-darwin)	8m 55s
pkg-pr-new	58s
api-docs	1m 32s
test-installation-pnpm (ubuntu-24.04-arm)	15s
test-installation-npm (windows-2025)	1m 8s
test-installation-npm (macos-15-intel)	39s
test-installation-pnpm (windows-2025)	30s
test-installation-npm (ubuntu-24.04-arm)	18s
test-installation-pnpm (macos-15-intel)	30s
test-installation-pnpm (macos-15)	22s
test-installation-pnpm (ubuntu-24.04)	21s
test-installation-npm (ubuntu-24.04)	16s
test-installation-npm (macos-15)	21s
test-integration-rewatch (ubuntu-24.04)	1m 20s
test-integration-rewatch (macos-15-intel)	3m 14s
test-integration-rewatch (windows-2025)	3m 4s
test-integration-rewatch (macos-15)	1m 58s
test-integration-rewatch (ubuntu-24.04-arm)	1m 15s
publish	0s
	1h 6m 43s

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