Downgrade dev-dep tokio to support MSRV 1.65 #278

Job	Run time
Verify MSRV	1m 3s
Style Checks (rustfmt)	12s
Style Check (clippy)	54s
Code Coverage (stable/ubuntu-latest)	3m 26s
README Format Check	1m 15s
Unit and Doc Tests (Rust Stable on ubuntu-latest)	18s
Integration Tests (Rust Stable with curl-client)	57s
Unit and Doc Tests (Rust Stable on windows-latest)	2m 26s
Integration Tests (Rust Stable with h1-client)	51s
Unit and Doc Tests (Rust Stable on macOS-latest)	20s
Integration Tests (Rust Stable with h1-client-rustls)	1m 13s
Unit and Doc Tests (Rust Beta on ubuntu-latest)	29s
Integration Tests (Rust Stable with hyper-client)	52s
Unit and Doc Tests (Rust Beta on windows-latest)	1m 5s
Integration Tests (Rust Stable with reqwest-client-rustls)	51s
Unit and Doc Tests (Rust Beta on macOS-latest)	25s
Integration Tests (Rust Stable with reqwest-client-native-tls)	26s
Unit and Doc Tests (Rust Nightly on ubuntu-latest)	1m 1s
Integration Tests (Rust Stable with reqwest-client-native-tls-vendored)	1m 49s
Unit and Doc Tests (Rust Nightly on windows-latest)	2m 1s
Unit and Doc Tests (Rust Nightly on macOS-latest)	53s
pages	0s
	22m 47s

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