fix another doc import

Author: folkertdev

src/builder.rs

@@ -20,6 +20,10 @@ use crate::types::{AsTypeRef, BasicType, IntMathType, FloatMathType, PointerType
 
 use std::marker::PhantomData;
 
+// imports used in documentation
+#[allow(unused_imports)]
+use crate::values::FunctionValue;
+
 #[derive(Debug)]
 pub struct Builder<'ctx> {
     builder: LLVMBuilderRef,