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>

.github/workflows/ci.yml

@@ -9,7 +9,7 @@ on:
 env:
   # Go version we currently use to build containerd across all CI.
   # Note: don't forget to update `Binaries` step, as it contains the matrix of all supported Go versions.
-  GO_VERSION: "1.21.5"
+  GO_VERSION: "1.21.6"
 
 permissions: # added using https://github.com/step-security/secure-workflows
   contents: read
@@ -209,7 +209,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-22.04, actuated-arm64-4cpu-16gb, macos-12, windows-2019, windows-2022]
-        go-version: ["1.20.12", "1.21.5"]
+        go-version: ["1.20.13", "1.21.6"]
     steps:
       - uses: actions/setup-go@v5
         with: