chore(deps): update dependency go to v1.25.6

| datasource     | package | from   | to     |
| -------------- | ------- | ------ | ------ |
| golang-version | go      | 1.25.5 | 1.25.6 |


Signed-off-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

go.mod

@@ -2,7 +2,7 @@ module github.com/cloudnative-pg/plugin-barman-cloud
 
 go 1.25.0
 
-toolchain go1.25.5
+toolchain go1.25.6
 
 require (
 	github.com/cert-manager/cert-manager v1.19.2