dockerfile: update frontend to 1.4

Signed-off-by: CrazyMax <crazy-max@users.noreply.github.com>

Dockerfile

@@ -1,4 +1,4 @@
-# syntax=docker/dockerfile:1.3
+# syntax=docker/dockerfile:1.4
 
 ARG GO_VERSION=1.17
 ARG DOCKERD_VERSION=20.10.8

docs/reference/buildx_build.md

@@ -429,7 +429,7 @@ Attribute keys:
 - `src`, `source` - Secret filename. `id` used if unset.
 
 ```dockerfile
-# syntax=docker/dockerfile:1.3
+# syntax=docker/dockerfile:1.4
 FROM python:3
 RUN pip install awscli
 RUN --mount=type=secret,id=aws,target=/root/.aws/credentials \
@@ -448,7 +448,7 @@ Attribute keys:
 - `env` - Secret environment variable. `id` used if unset, otherwise will look for `src`, `source` if `id` unset.
 
 ```dockerfile
-# syntax=docker/dockerfile:1.3
+# syntax=docker/dockerfile:1.4
 FROM node:alpine
 RUN --mount=type=bind,target=. \
   --mount=type=secret,id=SECRET_TOKEN \
@@ -480,7 +480,7 @@ authentication (e.g., cloning a private repository).
 Example to access Gitlab using an SSH agent socket:
 
 ```dockerfile
-# syntax=docker/dockerfile:1.3
+# syntax=docker/dockerfile:1.4
 FROM alpine
 RUN apk add --no-cache openssh-client
 RUN mkdir -p -m 0700 ~/.ssh && ssh-keyscan gitlab.com >> ~/.ssh/known_hosts

hack/dockerfiles/authors.Dockerfile

@@ -1,4 +1,4 @@
-# syntax=docker/dockerfile:1.3-labs
+# syntax=docker/dockerfile:1.4
 
 FROM alpine:3.14 AS gen
 RUN apk add --no-cache git

hack/dockerfiles/docs.Dockerfile

@@ -1,4 +1,4 @@
-# syntax=docker/dockerfile:1.3-labs
+# syntax=docker/dockerfile:1.4
 
 ARG GO_VERSION=1.17
 ARG FORMATS=md,yaml

hack/dockerfiles/lint.Dockerfile

@@ -1,4 +1,4 @@
-# syntax=docker/dockerfile:1.3
+# syntax=docker/dockerfile:1.4
 
 ARG GO_VERSION=1.17
 

hack/dockerfiles/vendor.Dockerfile

@@ -1,4 +1,4 @@
-# syntax=docker/dockerfile:1.3-labs
+# syntax=docker/dockerfile:1.4
 
 ARG GO_VERSION=1.17
 ARG MODOUTDATED_VERSION=v0.8.0