update to 28.3.0 (#623)

Bump the v28 docs to the 28.3.0 release:

- point the `28` version variables (`version`, `sourceVersion`, `dockerVersion`, `displayVersion`) at 28.3.0
- update the v28 entry in `update_api_docs.sh` to `28.3.0`
- regenerate `static/swagger-28.json` and `static/openapi3-28.json` from the `v28.3.0` tag, which picks up the updated `Deadline` and `Labels` descriptions from go-gitea/gitea#39869 and go-gitea/gitea#39873

Reviewed-on: https://gitea.com/gitea/docs/pulls/623
Reviewed-by: silverwind <[email protected]>

static/openapi3-28.json

@@ -5686,7 +5686,7 @@
             "x-go-name": "Description"
           },
           "due_on": {
-            "description": "Deadline is the updated due date for the milestone",
+            "description": "Deadline is the due date for the milestone, use null or empty string to remove the deadline",
             "format": "date-time",
             "type": "string",
             "x-go-name": "Deadline"
@@ -7416,7 +7416,7 @@
         "description": "IssueLabelsOption a collection of labels",
         "properties": {
           "labels": {
-            "description": "Labels can be a list of integers representing label IDs\nor a list of strings representing label names",
+            "description": "Labels can be a list of integers representing label IDs\nor a list of strings representing label names.\nIf a repository label and an organization label share a name,\nthe repository label is used.",
             "items": {},
             "type": "array",
             "x-go-name": "Labels"
@@ -11119,7 +11119,7 @@
       "url": "http://opensource.org/licenses/MIT"
     },
     "title": "Gitea API",
-    "version": "28.2.0"
+    "version": "28.3.0"
   },
   "openapi": "3.0.3",
   "paths": {