remove go1.21.9 from CI matrix

since go.mod got updated to go1.22, 1.22 is the minimum version to build
containerd. even if 1.21.9 is the version present on the host, go
command will build using 1.22.0 go version.

Signed-off-by: Akhil Mohan <[email protected]>

Author: akhilerm

.github/workflows/ci.yml

@@ -191,7 +191,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-22.04, actuated-arm64-4cpu-16gb, macos-12, windows-2019, windows-2022]
-        go-version: ["1.21.9", "1.22.2"]
+        go-version: ["1.22.2"]
         exclude:
           - os: ${{ github.repository != 'containerd/containerd' && 'actuated-arm64-4cpu-16gb' }}
     steps: