ci: Temporarily disable docs build #2411

Job	Run time
cargo +1.56 build	1m 10s
cargo bench	52s
cargo +1.36 build (futures-{core, io, sink})	31s
cargo +stable build	44s
cargo minimal-versions build	29s
cargo +beta build	46s
cargo +nightly build	42s
cargo build --target thumbv7m-none-eabi	34s
cargo test (ubuntu-latest)	2m 53s
cargo build --target thumbv6m-none-eabi	28s
cargo test (macos-latest)	5m 56s
cargo clippy	26s
cargo test (windows-latest)	4m 17s
cargo test (ubuntu-latest, aarch64-unknown-linux-gnu)	3m 36s
codegen	25s
cargo test (ubuntu-latest, armv7-unknown-linux-gnueabihf)	6m 23s
cargo hack check --feature-powerset	2m 45s
cargo test (ubuntu-latest, armv5te-unknown-linux-gnueabi)	6m 58s
cargo test (ubuntu-latest, i686-unknown-linux-gnu)	3m 11s
cargo fmt	12s
cargo miri test	7m 14s
cargo test -Z sanitizer=address	2m 50s
cargo test -Z sanitizer=memory	3m 41s
cargo test -Z sanitizer=thread	2m 13s
	59m 16s

Provide feedback