ci: use latest stable dockerfile syntax & rename docs Dockerfile (#9711)

* update dockerfiles to use latest stable syntax

Some Dockerfiles were pinned to a minor release, which meant they
wouldn't be updated to get the latest stable syntax (and fixes),
and one Dockerfile used the "labs" variant to use the HEREDOC syntax,
which has now been promoted to the stable syntax.

* docs: rename Dockerfile

There's no other Dockerfiles in the same path, so the "docs"
prefix was redundant.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

Dockerfile

@@ -1,4 +1,4 @@
-# syntax=docker/dockerfile:1.2
+# syntax=docker/dockerfile:1
 
 
 #   Copyright 2020 Docker Compose CLI authors

Makefile

@@ -99,7 +99,7 @@ docs: ## generate documentation
 	$(eval $@_TMP_OUT := $(shell mktemp -d -t dockercli-output.XXXXXXXXXX))
 	docker build . \
 	--output type=local,dest=$($@_TMP_OUT) \
-	-f ./docs/docs.Dockerfile \
+	-f ./docs/Dockerfile \
 	--target update
 	rm -rf ./docs/internal
 	cp -R "$($@_TMP_OUT)"/out/* ./docs/
@@ -108,7 +108,7 @@ docs: ## generate documentation
 .PHONY: validate-docs
 validate-docs: ## validate the doc does not change
 	@docker build . \
-	-f ./docs/docs.Dockerfile \
+	-f ./docs/Dockerfile \
 	--target validate
 
 .PHONY: check-dependencies

docs/Dockerfile

@@ -1,4 +1,4 @@
-# syntax=docker/dockerfile:1.3-labs
+# syntax=docker/dockerfile:1
 
 
 #   Copyright 2020 Docker Compose CLI authors

pkg/e2e/fixtures/build-test/secrets/Dockerfile

@@ -1,4 +1,4 @@
-# syntax=docker/dockerfile:1.2
+# syntax=docker/dockerfile:1
 
 
 #   Copyright 2020 Docker Compose CLI authors

pkg/e2e/fixtures/build-test/ssh/Dockerfile

@@ -1,4 +1,4 @@
-# syntax=docker/dockerfile:1.2
+# syntax=docker/dockerfile:1
 
 
 #   Copyright 2020 Docker Compose CLI authors