build(deps): bump golang from 1.25-alpine to 1.26-alpine in /docker

Bumps golang from 1.25-alpine to 1.26-alpine.

---
updated-dependencies:
- dependency-name: golang
  dependency-version: 1.26-alpine
  dependency-type: direct:production
...

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

docker/Dockerfile

@@ -4,7 +4,7 @@
 #
 
 # Pull the current golang-alpine image.
-FROM golang:1.25-alpine AS awg-go
+FROM golang:1.26-alpine AS awg-go
 
 # Install build-dependencies.
 RUN apk add --no-cache \