Update dependency go to v1.25.6

Signed-off-by: konflux-internal-p02 <170854209+konflux-internal-p02[bot]@users.noreply.github.com>

Author: konflux-internal-p02[bot]

demos/image_classification/go/go.mod

@@ -18,7 +18,7 @@ module ovmsclient
 
 go 1.23
 
-toolchain go1.21.9
+toolchain go1.25.6
 
 require (
 	github.com/golang/protobuf v1.5.3