Fix rotor cg calc without double counting Rhub

[gbarter]

Purpose

Fix bug identified in #693

Type of change

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (non-backwards-compatible fix or feature)
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Documentation update
• Maintenance update
• Other (please describe)

Testing

• I have run existing tests which pass locally with my changes
• I have added new tests or examples that prove my fix is effective or that my feature works
• I have added necessary documentation

[coveralls]

Pull Request Test Coverage Report for Build 21255680898

Details

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.005%) to 79.566%

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Files with Coverage Reduction	New Missed Lines	%
wisdem/commonse/utilization_eurocode.py	1	52.31%

Totals
Change from base Build 21030221407:	-0.005%
Covered Lines:	26463
Relevant Lines:	33259

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💛 - Coveralls