Update internal_utils.jl

Author: MilesCranmer

src/internal_utils.jl

@@ -5,7 +5,7 @@ library, but are used throughout.
 
 @generated function fieldnames_equal(::Type{T1}, ::Type{T2}) where {T1,T2}
     # Needs to be a generated function to ensure hardcoded
-    return static_fieldnames(T1) == static_fieldnames(T2)
+    return Base.propertynames(T1) == Base.propertynames(T2)
 end
 
 const SUPERSCRIPT_MAPPING = ('⁰', '¹', '²', '³', '⁴', '⁵', '⁶', '⁷', '⁸', '⁹')