Clarify overridden GC hint value for -Xms case

[amicic]

From:

https://eclipse.dev/openj9/docs/xxusegcstartuphints/

When enabled, this option overrides any initial heap size that is specified on the command line, for example by using the [-Xms](https://eclipse.dev/openj9/docs/xms/) option.

Suggestion:

The overridden value can only be larger than either default or explicitly set -Xms value. So, the above sentence would benefit from something like:

When enabled, this option overrides any initial heap size that is specified on the command line, for example by using the [-Xms](https://eclipse.dev/openj9/docs/xms/) option, while still obeying (-Xms, -Xmx) limits.

[Sreekala-Gopakumar]

@amicic - By "while still obeying (-Xms, -Xmx) limits", do you mean that the new value should be greater than -Xms set value and lesser than -Xmx set value?

[amicic]

@amicic - By "while still obeying (-Xms, -Xmx) limits", do you mean that the new value should be greater than -Xms set value and lesser than -Xmx set value?

Correct