switch ci build env version to 1.19

[MakDon]

switch ci build env version to 1.19, mentioned in this reply I've run the following commands to regenerate the files. It didn't make any difference.

docker run -v $(pwd):/grpc-gateway -w /grpc-gateway --rm ghcr.io/grpc-ecosystem/grpc-gateway/build-env:1.19 \
    /bin/bash -c 'make install && \
        make clean && \
        make generate'
docker run -itv $(pwd):/grpc-gateway -w /grpc-gateway --entrypoint /bin/bash --rm \
    ghcr.io/grpc-ecosystem/grpc-gateway/build-env:1.19 -c '\
        bazel run :gazelle -- update-repos -from_file=go.mod -to_macro=repositories.bzl%go_repositories && \
        bazel run :gazelle && \
        bazel run :buildifier'