[goog.object] Make unsafeClone a template T->T.
[goog.object] Make unsafeClone a template T->T.

Since cloning is supposed to return an equal object, I think the type signature should reflect that, otherwise every use of unsafeClone needs a cast.

RELNOTES[INC]: goog.object.unsafeClone has a T->T signature instead of *->*

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