Tweak default gradle options

If I look at the [gradlew file](https://github.com/exercism/kotlin/blob/main/exercises/practice/acronym/gradlew#L47) I see:

> DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'

To me, this looks like the exercises by default run with 64MB of memory. If that is correct, we should probaby update to a more reasonable amount.

Start with the referenced exercises/practice/acronym/gradlew file at line 47 and confirm how DEFAULT_JVM_OPTS affects exercise execution. Determine the appropriate default memory and whether the same wrapper setting appears elsewhere; done means the agreed default is updated consistently and the affected Gradle execution still works.

Written by the indexing model from the issue text.