Fix mismatched go versions (and AS casing)

[LeeBrotherston]

What was changed

• Updated the image for building from golang:1.22-bookworm to golang:1.23-bookworm in the Dockerfile
• Changed casing on AS statement to match the rest of the Dockerfile

Why?

• Dockerfile was using golang:1.22-bookworm as the builder image, but go.mod requires >= 1.23, and so the docker image build fails.
• The case of the AS keyword was causing a (non fatal) build error in Docker

Checklist

1. Closes n/a

2. How was this tested:
   docker build . the original version, observe the errors...

 => ERROR [builder 4/4] RUN go build ./cmd/temporal                                                                                                                                                             0.2s
------                                                                                                                                                                                                               
 > [builder 4/4] RUN go build ./cmd/temporal:
0.146 go: go.mod requires go >= 1.23 (running go 1.22.8; GOTOOLCHAIN=local)
------

 1 warning found (use docker --debug to expand):
 - FromAsCasing: 'as' and 'FROM' keywords' casing do not match (line 1)
Dockerfile:9
--------------------

docker build . this version and observe that these errors are not present

3. Any docs updates needed?

no.

[CLAassistant]

All committers have signed the CLA.

[cretz]

Thanks!