Bump golang from 1.20.3 to 1.21.1 in /docker/dev

Bumps golang from 1.20.3 to 1.21.1.

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

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

docker/dev/Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:1.20.3
+FROM golang:1.21.1
 
 ARG GOLANGCI_LINT_VERSION="1.53.3"
 ARG MOCKERY_VERSION="2.30.16"