Coverity analysis defect 120880: Unsigned compared against 0

Unsigned compared against 0

An unsigned value can never be negative, so this test will always evaluate the same way. An unsigned value can never be less than 0
/src/mongo/db/exec/sbe/expressions/expression.cpp:478: NO_EFFECT 120880 This greater-than-or-equal-to-zero comparison of an unsigned value is always true. "n >= 0UL".