Correct no-cache attribute to be a boolean

[rcjsuen]

The documentation is incorrect because no-cache needs to be a boolean.

$ docker buildx version
github.com/docker/buildx v0.29.1-desktop.1 28f6246ff24e2c05095e8741e48c48dcb2d3b4bc

target "default" {
  no-cache = 1
}

$ docker buildx bake --print default
[+] Building 0.0s (1/1) FINISHED
 => [internal] load local bake definitions                                                                                                                                  0.0s
 => => reading docker-bake.hcl 36B / 36B                                                                                                                                    0.0s
docker-bake.hcl:2
--------------------
   1 |     target "default" {
   2 | >>>   no-cache = 1
   3 |     }
   4 |
--------------------
ERROR: docker-bake.hcl:2,14-15: Unsuitable value type; Unsuitable value: bool required, but have number

[crazy-max]

Thanks!