[oneD] Remove hard-coded offset_T

[ischoegl]

Changes proposed in this pull request

Remove hard-coded offset in solution vector.

Checklist

• [ ] The pull request includes a clear description of this code change
• [ ] Commit messages have short titles and reference relevant issues
• [ ] Build passes (scons build & scons test) and unit tests address code coverage
• [ ] Style & formatting of contributed code follows contributing guidelines
• [ ] The pull request is ready for review