services/regulated-assets-approval-server: bump the Go version in Doc…

…kerfile that it was missed in stellar#5249 (stellar#5294)

### What

Bump the Go version in Dockerfile that it was missed in stellar#5249

### Why

The toolchain command in go.mod was requiring a Go version newer than the one in the Dockerfile, which was causing docker-build [to fail](https://stellarfoundation.slack.com/archives/C018BLTP2AU/p1714004215758189).

Toolchain command:
https://github.com/stellar/go/blob/ee9bbbf03be79bbac4000ea97b874ed010757b1b/go.mod#L3-L5

Container version incompatible with that toolchain version:
https://github.com/stellar/go/blob/ee9bbbf03be79bbac4000ea97b874ed010757b1b/services/regulated-assets-approval-server/docker/Dockerfile#L1

services/regulated-assets-approval-server/docker/Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:1.19.1 as build
+FROM golang:1.22-bullseye as build
 
 ADD . /src/regulated-assets-approval-server
 WORKDIR /src/regulated-assets-approval-server