Fix missing add_trust_anchors method due to lax rustls versioning #1697

Job	Run time
Lint	12s
Docs	20s
cargo-deny (aarch64-apple-ios)	19s
cargo-deny (aarch64-linux-android)	18s
Test	43s
cargo-deny (i686-pc-windows-gnu)	27s
Test (json)	41s
cargo-deny (i686-pc-windows-msvc)	23s
cargo-deny (i686-unknown-linux-gnu)	25s
Test (charset)	40s
cargo-deny (wasm32-unknown-unknown)	21s
Test (cookies)	1m 18s
cargo-deny (x86_64-apple-darwin)	25s
Test (socks-proxy)	37s
cargo-deny (x86_64-apple-ios)	27s
Test (native-certs)	56s
cargo-deny (x86_64-pc-windows-gnu)	19s
Test (gzip)	1m 13s
cargo-deny (x86_64-pc-windows-msvc)	24s
Test (brotli)	40s
cargo-deny (x86_64-unknown-linux-gnu)	18s
Test (http-interop)	1m 9s
cargo-deny (x86_64-unknown-redox)	18s
Test (tls)	1m 29s
Test (tls, json)	43s
Test (tls, charset)	44s
Test (tls, cookies)	47s
Test (tls, socks-proxy)	40s
Test (tls, native-certs)	43s
Test (tls, gzip)	48s
Test (tls, brotli)	1m 23s
Test (tls, http-interop)	45s
Test (native-tls)	1m 21s
Test (native-tls, json)	40s
Test (native-tls, charset)	48s
Test (native-tls, cookies)	46s
Test (native-tls, socks-proxy)	43s
Test (native-tls, native-certs)	47s
Test (native-tls, gzip)	42s
Test (native-tls, brotli)	52s
Test (native-tls, http-interop)	1m 32s
	29m 6s

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