Add go 1.20.6, 1.19.11

[CGA1123]

• Add go1.20.6
• Add go1.19.11
• go1.20 defaults to go1.20.6
• go1.19 defaults to go1.19.11

[joshwlewis]

The new binaries have been uploaded:

$ sbin/sync-files.sh golangci-lint-1.45.0-linux-amd64.tar.gz
Getting bucket credentials
                          Syncing contents of s3:https://heroku-golang-prod/ to /Users/josh.lewis/code/heroku-buildpack-go/file-cache.
                                            Ensuring the correct versions of all files specified in files.json
                          Ignored file: golangci-lint-1.45.0-linux-amd64.tar.gz
                                                                               All files verified, syncing to s3

                            Completed 256.0 KiB/237.8 MiB (1.6 MiB/s) with 2 file(s)upload: ./go1.19.11.linux-amd64.tar.gz to s3:https://heroku-golang-prod/go1.19.11.linux-amd64.tar.gz
upload: ./go1.20.6.linux-amd64.tar.gz to s3:https://heroku-golang-prod/go1.20.6.linux-amd64.tar.gz

[joshwlewis]

Looks great, thanks!