ci: pin hashbrown for msrv job (#2488) #2211

Job	Run time
Check Style	11s
Android	30s
MSRV	1m 2s
linux / nightly	1m 20s
linux / stable	51s
linux / beta	1m 18s
WASM	53s
unstable features	59s
macOS / stable	1m 42s
windows / stable-x86_64-msvc	4m 5s
windows / stable-i686-msvc	4m 2s
windows / stable-x86_64-gnu	4m 30s
windows / stable-i686-gnu	5m 6s
feat.: default-tls disabled	1m 7s
feat.: rustls-tls	1m 12s
feat.: rustls-tls-manual-roots	1m 0s
feat.: rustls-tls-native-roots	1m 15s
feat.: rustls-tls-no-provider	1m 1s
feat.: native-tls	1m 14s
feat.: default-tls and rustls-tls	1m 24s
feat.: rustls-tls and rustls-tls-no-provider	59s
feat.: cookies	1m 19s
feat.: blocking	1m 7s
feat.: blocking only	1m 20s
feat.: gzip	1m 19s
feat.: brotli	1m 24s
feat.: deflate	1m 20s
feat.: json	1m 19s
feat.: multipart	1m 23s
feat.: stream	51s
feat.: socks/default-tls	1m 15s
feat.: socks/rustls-tls	48s
feat.: hickory-dns	1m 24s
feat.: zstd	55s
Docs	1m 50s
CI is green	1s
	53m 16s

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