[FXC-3416] Support write single file output for surface outputs in paraview format

[awccoppFC]

Removed validation check for write single file output surface output preventing paraview format

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Note

Low Risk
Removes a validation guardrail and expands supported configuration; risk is limited to potential downstream solver/runtime incompatibility if Paraview single-file writing isn’t actually supported.

Overview
SurfaceOutput no longer raises/ warns when write_single_file=True is used with output_format="paraview" or "both", effectively enabling single-file surface outputs for Paraview.

Tests are updated to reflect the new behavior by removing the expected validation error and asserting these configurations now validate successfully.

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