chore(deps): update image golang to v1.21.5 (#59)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

Dockerfile

@@ -1,7 +1,7 @@
 # syntax=docker/dockerfile:1
 
 ## Build stage
-FROM golang:1.21.4-alpine as build
+FROM golang:1.21.5-alpine@sha256:feceecc0e1d73d085040a8844de11a2858ba4a0c58c16a672f1736daecc2a4ff as build
 
 RUN apk --no-cache add ca-certificates tzdata
 RUN addgroup --gid 65532 kani && \