Upgrade buildbox gci (#48741)

The current verson of GCI in the buildbox treats the Go 1.23 `iter` package
as an external package rather than part of the stdlib. This patch updates gci
to a version that orders it correctly.

build.assets/Dockerfile

@@ -318,7 +318,7 @@ RUN go install "github.com/gogo/protobuf/protoc-gen-gogofast@$GOGO_PROTO_TAG"
 RUN go install github.com/google/[email protected]
 
 # Install GCI.
-RUN go install github.com/daixiang0/gci@v0.12.3
+RUN go install github.com/daixiang0/gci@v0.13.5
 
 # Install gotestsum.
 RUN go install gotest.tools/[email protected]