Fix label not being unique error on windows

[Dtenwolde]

Almost all tests seem to fail on Windows in the CI as follows:

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Query unexpectedly failed! (D:/a/duckpgq-extension/duckpgq-extension/test/sql/altering_table.test:34)!
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-CREATE PROPERTY GRAPH pg
VERTEX TABLES (
    Student PROPERTIES ( id, name ) LABEL Person,
    School LABEL SCHOOL
    )
EDGE TABLES (
    know    SOURCE KEY ( src ) REFERENCES Student ( id )
            DESTINATION KEY ( dst ) REFERENCES Student ( id )
            LABEL Knows,
    studyAt SOURCE KEY ( personId ) REFERENCES Student ( id )
            DESTINATION KEY ( SchoolId ) REFERENCES School ( id )
            LABEL StudyAt
    );
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Constraint Error: Label school is not unique, make sure all labels are unique