fix: update .golangci.yml to v2 config format

golangci-lint v2 requires version: "2" at the top level, linters.settings
(not linters-settings), and issues.exclusions.rules (not issues.exclude-rules).
Also removed gosimple and unused which are now merged into staticcheck.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

.golangci.yml

@@ -1,25 +1,24 @@
+version: "2"
+
 linters:
   enable:
     - errcheck
     - govet
     - staticcheck
-    - gosimple
     - ineffassign
-    - unused
     - errorlint
     - gocritic
     - revive
-
-linters-settings:
-  revive:
-    rules:
-      - name: exported
-        disabled: true
+  settings:
+    revive:
+      rules:
+        - name: exported
+          disabled: true
 
 issues:
-  exclude-rules:
-    # Test files can use dot-imports and assertion helpers freely
-    - path: _test\.go
-      linters:
-        - errcheck
-        - gocritic
+  exclusions:
+    rules:
+      - path: _test\.go
+        linters:
+          - errcheck
+          - gocritic