chore(deps): bump golang from 1.21.2-alpine to 1.21.3-alpine (#2787)

Bumps golang from 1.21.2-alpine to 1.21.3-alpine.

Dockerfile.standalone

@@ -1,6 +1,6 @@
 # This version of Dockerfile is for building without external dependencies.
 # Build a multi-platform image e.g. `docker buildx build --push --platform linux/arm64,linux/amd64 --tag external-secrets:dev --file Dockerfile.standalone .`
-FROM golang:1.21.2-alpine AS builder
+FROM golang:1.21.3-alpine AS builder
 ARG TARGETOS
 ARG TARGETARCH
 ENV CGO_ENABLED=0 GOOS=${TARGETOS} GOARCH=${TARGETARCH}