During JDK-8329223 code review (https://github.com/openjdk/jdk/pull/18539/)

@lgxbslgx suggested some comment cleanup:

```
The comment shown below seems strange. Can it be removed?

    // The generation minimums and the overall heap minimum should
    // be within one generation alignment.


The warning message shown below can be more consistent with this newly added one.

      log_warning(gc, ergo)("Inconsistency between maximum heap size and maximum "
                            "generation sizes: using maximum heap = " SIZE_FORMAT
                            ", -XX:OldSize flag is being ignored",
                            MaxHeapSize);

```