Fix forest size for symmetry dimensions

PR Summary

This PR fixes a bug in the hyper rectangular forest generation routine.

[ ] Code passes cpplint
[ ] New features are documented.
[ ] Adds a test for any bugs fixed. Adds tests for new features.
[ ] Code is formatted
[ ] Changes are summarized in CHANGELOG.md
[ ] Change is breaking (API, behavior, ...)
- [ ] Change is additionally added to CHANGELOG.md in the breaking section
- [ ] PR is marked as breaking
- [ ] Short summary API changes at the top of the PR (plus optionally with an automated update/fix script)
[ ] CI has been triggered on Darwin for performance regression tests.
[ ] Docs build
[ ] (@lanl.gov employees) Update copyright on changed files