docs: fix ContrMod docstring (real vectors, not complex)

[sankalpsthakur]

Summary

toFin1dℝFun was documented as an equivalence between ContrℝModule and complex-valued functions. The type is ContrMod d ≃ (Fin 1 ⊕ Fin d → ℝ). Update that docstring and the other stale ContrℝModule names in this file.

Validation

• Doc comments now match ContrMod and ℝ in Physlib/Relativity/Tensors/RealTensor/Vector/Pre/Modules.lean.

Fixes #1508

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[jstoobysmith]

Approved - many thanks for this fix.