fix: Do not depend on dune in dune-project in dune init template

Dune automatically adds the right constraint anyway, with the right
version constraint. All Dune project implicitely depend on Dune anyway
and the tests show that the opam files correctly include Dune.

This helps with #11106 but also avoids the bug where Dune couldn't solve
a package because it depended on Dune and in the Dune Package Management
we explicitely remove the dependency.

Signed-off-by: Marek Kubica <marek@tarides.com>

bin/dune_init.ml

@@ -404,7 +404,6 @@ module Component = struct
               [ { Package_dependency.name = Package.Name.of_string "ocaml"
                 ; constraint_ = None
                 }
-              ; { name = Package.Name.of_string "dune"; constraint_ = None }
               ]
         in
         let packages = Package.Name.Map.singleton (Package.name package) package in

test/blackbox-tests/test-cases/dune-init.t/run.t

@@ -357,7 +357,7 @@ In particular, the `dune-project` file has the expected content:
    (name new_exec_proj)
    (synopsis "A short synopsis")
    (description "A longer description")
-   (depends ocaml dune)
+   (depends ocaml)
    (tags
     ("add topics" "to describe" your project)))
 
@@ -384,8 +384,8 @@ And the opam file will be generated as expected
   doc: "https://url/to/documentation"
   bug-reports: "https://github.com/username/reponame/issues"
   depends: [
-    "ocaml"
     $dune {>= "3.17"}
+    "ocaml"
     "odoc" {with-doc}
   ]
   build: [
@@ -467,7 +467,7 @@ In particular, the `dune-project` file has the expected content:
    (name new_lib_proj)
    (synopsis "A short synopsis")
    (description "A longer description")
-   (depends ocaml dune)
+   (depends ocaml)
    (tags
     ("add topics" "to describe" your project)))
 
@@ -494,8 +494,8 @@ And the opam file will be generated as expected
   doc: "https://url/to/documentation"
   bug-reports: "https://github.com/username/reponame/issues"
   depends: [
-    "ocaml"
     "dune" {>= "3.17"}
+    "ocaml"
     "odoc" {with-doc}
   ]
   build: [