fix(security/UNKNOWN/operator): Update go toolchain directive to v1.26.5 [SECURITY]

| datasource     | package | from   | to     |
| -------------- | ------- | ------ | ------ |
| golang-version | go      | 1.26.4 | 1.26.5 |


Signed-off-by: renovate-sh-app[bot] <219655108+renovate-sh-app[bot]@users.noreply.github.com>

Author: renovate-sh-app[bot]

operator/go.mod

@@ -2,7 +2,7 @@ module github.com/grafana/loki/operator
 
 go 1.25.7
 
-toolchain go1.26.4
+toolchain go1.26.5
 
 require (
 	dario.cat/mergo v1.0.2