Update osltoyrenderer.cpp: auto-detect output variable -- doesn't need to be Cout if there's only on

[lunakhan]

auto-detect output variable -- doesn't need to be Cout if there's only one

Description

Tests

Checklist:

• [ ] I have read the contribution guidelines.
• [ ] I have updated the documentation, if applicable.
• [ ] I have ensured that the change is tested somewhere in the testsuite (adding new test cases if necessary).
• [ ] My code follows the prevailing code style of this project. If I haven't already run clang-format v17 before submitting, I definitely will look at the CI test that runs clang-format and fix anything that it highlights as being nonconforming.