Fixed a logical typo in the Johnson Cook strength model

[swiggins8]

Fixed a logical typo in the Johnson Cook strength model that would cause the temperature dependence to behave nonphysically.

Summary

This PR fixes a line in the Johnson Cook strength model that would cause the temperature dependence within the model to behave nonphysically.

Specifically the homologous temperature would get artificially clamped to 1 / (Tmelt - Troom) not allowing proper yielding at temperatures above the room temperature. For temperatures below room temperature updated equation results in the same homologous temperature Tstar.

Line updated from:
const auto Tstar = std::max(0.0, std::min(1.0, T(i) - mTroom)/(mTmelt - mTroom));
To:
const auto Tstar = std::max(0.0, std::min(1.0, ((T(i) - mTroom)/(mTmelt - mTroom))));

I have performed a test of my own and the yield strength now behaves more physically, without any nonphysical yield strengths emerging when a material heats up.

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ToDo :

• Annotate RELEASE_NOTES.md with notable changes.
• Create LLNLSpheral PR pointing at this branch. (PR#)
• LLNLSpheral PR has passed all tests.