Use correct response code in push mirror creation response in v1_json.tmpl (#25476) (#25571)

Backport #25476 by @GeorgDangl

In the process of doing a bit of automation via the API, we've
discovered a _small_ issue in the Swagger definition. We tried to create
a push mirror for a repository, but our generated client raised an
exception due to an unexpected status code.

When looking at this function:

3c7f5ed7b5/routers/api/v1/repo/mirror.go (L236-L240)

We see it defines `201 - Created` as response:

3c7f5ed7b5/routers/api/v1/repo/mirror.go (L260-L262)

But it actually returns `200 - OK`:

3c7f5ed7b5/routers/api/v1/repo/mirror.go (L373)

So I've just updated the Swagger definitions to match the code😀

Co-authored-by: Georg Dangl <10274404+GeorgDangl@users.noreply.github.com>

routers/api/v1/repo/mirror.go

@@ -258,7 +258,7 @@ func AddPushMirror(ctx *context.APIContext) {
 	//   schema:
 	//     "$ref": "#/definitions/CreatePushMirrorOption"
 	// responses:
-	//   "201":
+	//   "200":
 	//     "$ref": "#/responses/PushMirror"
 	//   "403":
 	//     "$ref": "#/responses/forbidden"

templates/swagger/v1_json.tmpl

@@ -10729,7 +10729,7 @@
           }
         ],
         "responses": {
-          "201": {
+          "200": {
             "$ref": "#/responses/PushMirror"
           },
           "400": {