Bug fix: OpenFAST ServoDyn input file syntax

[rafmudaf]

Pull-request type:

• Bug fix
• Documentation update
• Feature enhancement

Description of the pull-request

Removes an extra and invalid section of the ServoDyn input file for the OpenFAST-coupled regression tests.

Tested with OpenFAST standalone (switched the inflow conditions to steady wind) and it runs successfully after compiling the controller library.

Checklist

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All pull requests

• Builds successfully (must test on at least one system/compiler combination)
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  • Compilers
    • GCC
    • LLVM/Clang
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• Compiles without warnings
• Passes all unit tests
• Passes all regression tests
• Documentation builds without errors

For new code updates

• Documentation updates - additions to user, theory, and verification manuals
• New unit tests providing coverage for new code, bug fixes etc.
• New regression tests exercising the new code

[rafmudaf]

FWIW I've improved the documentation in OpenFAST because of these failing tests in Nalu, so its not been for nothing :)
OpenFAST/openfast#1101