all: release v1.28.1
all: release v1.28.1

Change-Id: I2987633792a1429079cfebdf4c03d5629e4a448a
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/419934
Reviewed-by: Michael Stapelberg <97e0203ad32d728c266b6422d4bd97c18b9b600f@google.com>

protocolbuffers/protobuf-go,protocolbuffers/protobuf-go