tests: fix test logic for x/crypto 0.37.0 change

In golang.org/x/crypto v0.37.0+, golang/crypto#254 has
been merged, which means x/crypto/ssh/knownhosts can return multiple keys of
the same type in its KeyError.Want slice.

Here in skeema/knownhosts, our logic already handles that properly, and
ensures that HostKeyAlgorithms is de-duped; see commit 3a35d9f from Sep 2023.
However, in that commit I failed to adjust one of the tests, which examines
the returned keys (which are intentionally not de-duped) rather than the
algorithms (which are de-duped).

This commit fixes the test to now work properly with x/crypto v0.37.0+.

Author: evanelias

knownhosts_test.go

@@ -90,7 +90,7 @@ func TestHostKeys(t *testing.T) {
 		"only-rsa.example.test:22":     {"ssh-rsa"},
 		"only-ecdsa.example.test:22":   {"ecdsa-sha2-nistp256"},
 		"only-ed25519.example.test:22": {"ssh-ed25519"},
-		"multi.example.test:2233":      {"ssh-rsa", "ecdsa-sha2-nistp256", "ssh-ed25519"},
+		"multi.example.test:2233":      {"ssh-rsa", "ecdsa-sha2-nistp256", "ssh-ed25519", "ssh-ed25519"},
 		"192.168.1.102:2222":           {"ecdsa-sha2-nistp256", "ssh-ed25519"},
 		"unknown-host.example.test":    {}, // host not in file
 		"multi.example.test:22":        {}, // different port than entry in file