fix: revert .golangci.yml to v1 format for CI compatibility

CI uses golangci-lint v1.x which doesn't support v2 config format

.golangci.yml

@@ -1,30 +1,21 @@
-version: "2"
-
 run:
   timeout: 5m
 
+linters-settings:
+  goimports:
+    local-prefixes: github.com/luxfi/mpc
+
 linters:
   enable:
+    - goimports
     - govet
     - ineffassign
     - misspell
     - unconvert
-  disable:
-    - errcheck
-
-formatters:
-  enable:
-    - goimports
-  settings:
-    goimports:
-      local-prefixes:
-        - github.com/luxfi/mpc
 
 issues:
   exclude-dirs:
     - vendor
     - .git
-  exclude-files:
-    - ".*_test.go"
   max-issues-per-linter: 0
   max-same-issues: 0