chore: fix leftover update to go 1.26.1 (#265)

Follow-up of #263

Signed-off-by: Ignasi Barrera <ignasi@tetrate.io>

Author: nacx

extensions/composer/Dockerfile.plugin

@@ -8,7 +8,7 @@
 # Dockerfile (e.g., Dockerfile.custom) instead of editing this file.
 
 # Build the manager binary
-FROM golang:1.25.7 AS builder
+FROM golang:1.26.1 AS builder
 
 ARG EXTENSION_PATH