Update registry Docker tag to v3

| datasource | package  | from | to |
| ---------- | -------- | ---- | -- |
| docker     | registry | 2    | 3  |


Signed-off-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/docker-openresty.yml

@@ -20,7 +20,7 @@ jobs:
     runs-on: ubuntu-24.04
     services:
       registry:
-        image: registry:2
+        image: registry:3
         ports:
           - 5000:5000
     steps:

.github/workflows/docker.yml

@@ -23,7 +23,7 @@ jobs:
     runs-on: ubuntu-24.04
     services:
       registry:
-        image: registry:2
+        image: registry:3
         ports:
           - 5000:5000
     strategy: