Update dependency go to 1.26

Generated by renovateBot

Author: renovate[bot]

.github/workflows/conformance.yml

@@ -28,7 +28,7 @@ jobs:
       - name: Setup Go
         uses: actions/setup-go@v6
         with:
-          go-version: "1.25" # auto-update/latest-go-version
+          go-version: "1.26" # auto-update/latest-go-version
           cache: true
 
       - name: Run conformance test