fix(ci): upgrade golangci-lint-action to v7 for Go 1.25 compatibility

golangci-lint-action v6 installs v1.x built with Go 1.24, which cannot
lint a Go 1.25 module. v7 uses golangci-lint v2 built with Go 1.25+.

Author: SoulKyu

.github/workflows/ci.yml

@@ -36,9 +36,7 @@ jobs:
           cache: true
 
       - name: Run golangci-lint
-        uses: golangci/golangci-lint-action@v6
-        with:
-          version: latest
+        uses: golangci/golangci-lint-action@v7
 
   docs-check:
     name: Docs up to date