made KeychainManager immutable

[ci skip]

main/commons/src/main/java/org/cryptomator/common/keychain/KeychainManager.java

@@ -19,7 +19,7 @@ import java.util.Arrays;
 public class KeychainManager implements KeychainAccessProvider {
 
 	private final ObjectExpression<KeychainAccessProvider> keychain;
-	private LoadingCache<String, BooleanProperty> passphraseStoredProperties;
+	private final LoadingCache<String, BooleanProperty> passphraseStoredProperties;
 
 	@Inject
 	KeychainManager(ObjectExpression<KeychainAccessProvider> selectedKeychain) {