clarify API stability note in the "core" module
* The strategies here are not meant to be used directly.
* Their API is not optimized for end user friendliness, but for integration correctness.
* The core abstraction is {@link io.smallrye.faulttolerance.core.FaultToleranceStrategy}; each strategy implements that.
- * API stability is <b>not</b> guaranteed!
+ * API stability in this package and all its subpackages is <b>not</b> guaranteed!
*/
package io.smallrye.faulttolerance.core;
