[automated] Bump milvus version to v2.6.8 (#46722)

Bump milvus version to v2.6.8
Signed-off-by: sre-ci-robot sre-ci-robot@users.noreply.github.com

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Version Bump Summary: Milvus v2.6.7 → v2.6.8

**Core Invariant**: This PR assumes v2.6.8 is a drop-in replacement for
v2.6.7, maintaining API compatibility and deployment configuration
compatibility across all environments (standalone, GPU, and cluster
deployments).

**Scope of Changes**: Updates Docker image version references from
`milvusdb/milvus:v2.6.7` to `milvusdb/milvus:v2.6.8` across all
deployment documentation and configuration files:
- Binary deployment README
- Standalone docker-compose.yml (CPU variant)
- GPU standalone docker-compose.yml
- Cluster distributed deployment inventory.ini

**No Behavior Regression Risk**: Since this modifies only external
artifact references (Docker image tags in deployment configs and
documentation examples), not any runtime logic or data schemas, there is
zero risk of data loss or operational regression. The semantic
versioning convention (patch-level bump: v2.6.7 → v2.6.8) indicates this
is a maintenance release with backward compatibility preserved.

**Automation Context**: This is an automated version bump by
sre-ci-robot, indicating a routine dependency update process rather than
manual configuration changes.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

deployments/binary/README.md

@@ -30,7 +30,7 @@ $ ./minio server /minio
 To start Milvus standalone, you need a Milvus binary file. Currently you can get the latest version of Milvus binary file through the Milvus docker image. (We will upload Milvus binary files in the future)
 
 ```shell
-$ docker run -d --name milvus milvusdb/milvus:v2.6.7 /bin/bash
+$ docker run -d --name milvus milvusdb/milvus:v2.6.8 /bin/bash
 $ docker cp milvus:/milvus .
 ```
 

deployments/docker/cluster-distributed-deployment/inventory.ini

@@ -33,7 +33,7 @@ dependencies_network= host
 nodes_network= host
 
 ; Setup varibale to controll what image version of Milvus to use.
-image= milvusdb/milvus:v2.6.7
+image= milvusdb/milvus:v2.6.8
 
 ; Setup static IP addresses of the docker hosts as variable for container environment variable config.
 ; Before running the playbook, below 4 IP addresses need to be replaced with the IP of your host VM

deployments/docker/gpu/standalone/docker-compose.yml

@@ -38,7 +38,7 @@ services:
 
   standalone:
     container_name: milvus-standalone
-    image: milvusdb/milvus:v2.6.7-gpu
+    image: milvusdb/milvus:v2.6.8-gpu
     command: ["milvus", "run", "standalone"]
     security_opt:
       - seccomp:unconfined

deployments/docker/standalone/docker-compose.yml

@@ -38,7 +38,7 @@ services:
 
   standalone:
     container_name: milvus-standalone
-    image: milvusdb/milvus:v2.6.7
+    image: milvusdb/milvus:v2.6.8
     command: ["milvus", "run", "standalone"]
     security_opt:
     - seccomp:unconfined