golangci-lint: Fix deprecation warnings

There were a couple of deprecation warnings after bumping golangci-lint
version:

    WARN [linters_context] copyloopvar: this linter is disabled because the Go version (1.20) of your project is lower than Go 1.22
    WARN [config_reader] The configuration option `run.skip-files` is deprecated, please use `issues.exclude-files`.
    WARN [config_reader] The configuration option `linters.gci.local-prefixes` is deprecated, please use `prefix()` inside `linters.gci.sections`.
    WARN [config_reader] The configuration option `linters.staticcheck.go` is deprecated, please use global `run.go`.
    WARN [config_reader] The configuration option `linters.stylecheck.go` is deprecated, please use global `run.go`.

Author: mandre

.golangci.yml

@@ -5,7 +5,8 @@ linters:
   - asciicheck
   - bidichk
   - bodyclose
-  - copyloopvar
+  # Commented out as this linter doesn't work against go 1.20 projects
+  # - copyloopvar
   - cyclop
 #  - depguard
   - dogsled
@@ -56,7 +57,10 @@ linters-settings:
     # TODO(sbuerin) fix remaining findings and set to 20 afterwards
     max-complexity: 30
   gci:
-    local-prefixes: sigs.k8s.io/cluster-api-provider-openstack
+    sections:
+      - standard
+      - default
+      - prefix(sigs.k8s.io/cluster-api-provider-openstack)
   gocritic:
     enabled-tags:
       - diagnostic
@@ -129,10 +133,6 @@ linters-settings:
   nolintlint:
     # https://github.com/golangci/golangci-lint/issues/3228
     allow-unused: true
-  staticcheck:
-    go: "1.20"
-  stylecheck:
-    go: "1.20"
   nestif:
     # minimal complexity of if statements to report, 5 by default
     # TODO(sbuerin) fix remaining findings and set to 5 after:
@@ -171,12 +171,13 @@ issues:
     - stylecheck
     text: "ST1003: should not use underscores in Go names;"
     path: .*(api|types)\/.*\/.*conversion.*\.go$
+  exclude-files:
+    - "zz_generated.*\\.go$"
 
 run:
   timeout: 10m
   build-tags:
   - e2e
+  go: "1.20"
 
-  skip-files:
-    - "zz_generated.*\\.go$"
   allow-parallel-runners: true