update to go1.21.6, go1.20.13

go1.21.6 (released 2024-01-09) includes fixes to the compiler, the runtime, and
the crypto/tls, maps, and runtime/pprof packages. See the Go 1.21.6 milestone on
our issue tracker for details:

- https://github.com/golang/go/issues?q=milestone%3AGo1.21.6+label%3ACherryPickApproved
- full diff: https://github.com/golang/go/compare/go1.21.5...go1.21.6

go1.20.13 (released 2024-01-09) includes fixes to the runtime and the crypto/tls
package. See the Go 1.20.13 milestone on our issue tracker for details:

- https://github.com/golang/go/issues?q=milestone%3AGo1.20.13+label%3ACherryPickApproved
- full diff: https://github.com/golang/go/compare/go1.20.12...go1.20.13

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

contrib/fuzz/oss_fuzz_build.sh

@@ -43,11 +43,11 @@ go run main.go $SRC/containerd/images
 
 apt-get update && apt-get install -y wget
 cd $SRC
-wget --quiet https://go.dev/dl/go1.21.5.linux-amd64.tar.gz
+wget --quiet https://go.dev/dl/go1.21.6.linux-amd64.tar.gz
 
 mkdir temp-go
 rm -rf /root/.go/*
-tar -C temp-go/ -xzf go1.21.5.linux-amd64.tar.gz
+tar -C temp-go/ -xzf go1.21.6.linux-amd64.tar.gz
 mv temp-go/go/* /root/.go/
 cd $SRC/containerd