Always use bcrypt to hash the WebAuthn MFA API's api secret

Our MFA APIs use bcrypt for that, and at some point the
`PASSWORD_DEFAULT` may change for PHP. This commit's code change
protects this code from breaking when the default PHP password hashing
algorithm does change.

application/features/bootstrap/AuthenticationContext.php

@@ -81,7 +81,7 @@ public function weHaveTheWrongPasswordForTheWebauthnMfaApi()
 
     protected function setWebAuthnApiSecretTo(string $newPlainTextApiSecret)
     {
-        $newHashedApiSecret = password_hash($newPlainTextApiSecret, PASSWORD_DEFAULT);
+        $newHashedApiSecret = password_hash($newPlainTextApiSecret, PASSWORD_BCRYPT);
         $dynamoDbClient = new DynamoDbClient([
             'region'   => getenv('AWS_DEFAULT_REGION'),
             'endpoint' => getenv('AWS_ENDPOINT'),