Update go version in Makefile to 1.29.9

Author: Avritt Rohwer

Makefile

@@ -24,7 +24,7 @@ ALL_ARCH ?= amd64 arm arm64 ppc64le s390x
 # The output type could either be docker (local), or registry.
 OUTPUT_TYPE ?= docker
 GO_TOOLCHAIN ?= golang
-GO_VERSION ?= 1.21.6
+GO_VERSION ?= 1.21.9
 BASEIMAGE ?= gcr.io/distroless/static-debian11:nonroot
 
 ifeq ($(GOPATH),)