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docs: Fix opendal rust core's README not align with new vision #8469

Job	Run time
build-java-doc	22s
build-nodejs-doc	21s
build-python-doc	3m 17s
build-rust-doc	3m 48s
build-c-doc	27s
build-cpp-doc	42s
build-haskell-doc	2m 28s
build-lua-doc	16s
build-dav-server-opendalfs-doc	48s
build-fuse3-opendal-doc	50s
build-object-store-opendal-doc	48s
build-parquet-opendal-doc	50s
build-ocaml-doc	4m 53s
build-unftp-sbe-opendal-doc	1m 14s
build-virtiofs-opendal-doc	47s
build-opendal-compat-doc	56s
build-website	1m 24s
	24m 11s

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