build(deps): bump golang from 1.21.5 to 1.21.6

Bumps golang from 1.21.5 to 1.21.6.

---
updated-dependencies:
- dependency-name: golang
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Dockerfile

@@ -1,5 +1,5 @@
 # Get Golang for builder
-FROM golang:1.21.5 as builder
+FROM golang:1.21.6 as builder
 
 # Set the working directory
 WORKDIR /go/src/github.com/BuxOrg/bux-server