chore: bump patch version 0.15.4 (#2002)

Co-authored-by: daviderli614 <[email protected]>

Author: github-actions[bot]

variables/variables-0.15.ts

@@ -1,5 +1,5 @@
 export const variables = {
-  greptimedbVersion: 'v0.15.3',
+  greptimedbVersion: 'v0.15.4',
   prometheusVersion: 'v2.52.0',
   nodeExporterVersion: 'v1.8.0',
   goSdkVersion: 'v0.6.2',