Update cimg/base Docker tag to v2025.06

Author: renovate[bot]

.circleci/config.yml

@@ -2,7 +2,7 @@ version: 2
 jobs:
   docker-ubuntu-vnc:
     docker:
-      - image: cimg/base:2025.05
+      - image: cimg/base:2025.06
     steps:
       - checkout
       - setup_remote_docker
@@ -15,7 +15,7 @@ jobs:
 
   docker-ubuntu-vnc-java:
     docker:
-      - image: cimg/base:2025.05
+      - image: cimg/base:2025.06
     steps:
       - checkout
       - setup_remote_docker
@@ -28,7 +28,7 @@ jobs:
 
   docker-ubuntu-vnc-go:
     docker:
-      - image: cimg/base:2025.05
+      - image: cimg/base:2025.06
     steps:
       - checkout
       - setup_remote_docker