Add PHPStan false positive to baseline

PHPStan now looks closely at the types passed into my_convert_encoding
and tries to model its behavior based on the parameter types passed in.
See phpstan/phpstan#13064
and phpstan/phpstan-src#4010

We'd rather keep our code as-is (adhering to the [PHP documentation for
mb_convert_encoding](https://www.php.net/manual/en/function.mb-convert-encoding.php))
than thinking about the complex possible behavior.

Author: gbirke

phpstan-baseline.neon

@@ -15,3 +15,6 @@ parameters:
         - message: "#^Call to an undefined method Symfony\\\\Component\\\\Config\\\\Definition\\\\Builder\\\\NodeDefinition\\:\\:arrayPrototype\\(\\)\\.$#"
           count: 1
           path: src/Services/PayPal/PayPalPaymentProviderAdapterConfigSchema.php
+        - message: "#^Strict comparison using === between non-empty-array and false will always evaluate to false\\.$#"
+          count: 1
+          path: src/Services/KontoCheck/KontoCheckBankDataGenerator.php