MM-57245: Bump up Go version to 1.21 (#26512)

* MM-57245: Bump up Go version to 1.21

https://mattermost.atlassian.net/browse/MM-57245
```release-note
NONE
```

.github/workflows/codeql-analysis.yml

@@ -42,7 +42,7 @@ jobs:
     - name: Setup go
       uses: actions/setup-go@v2
       with:
-        go-version: '1.20'
+        go-version: '1.21'
       if: ${{ matrix.language == 'go' }}