fix: require Go 1.26.6 to resolve GO-2026-5026-stdlib (#3351)

Co-authored-by: chainloop-platform[bot] <266818671+chainloop-platform[bot]@users.noreply.github.com>

Author: chainloop-platform[bot]

go.mod

@@ -1,6 +1,6 @@
 module github.com/chainloop-dev/chainloop
 
-go 1.26.5
+go 1.26.6
 
 require (
 	cloud.google.com/go/secretmanager v1.21.0