.github: update go to 1.25

Author: paralin

.github/workflows/tests.yml

@@ -16,7 +16,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        go: ['1.21']
+        go: ['1.25']
     timeout-minutes: 10
     steps:
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2