Fix up copyright date change

SuperQ · SuperQ · commit dffe507aadab · 2022-07-27T14:11:01.000+02:00
Return the copyright date in `collector/cpu_openbsd.go` to the original value. Minor change revert on #1971 Signed-off-by: Ben Kochie <superq@gmail.com>
diff --git a/collector/cpu_openbsd.go b/collector/cpu_openbsd.go
@@ -1,4 +1,4 @@
-// Copyright 2020 The Prometheus Authors
+// Copyright 2018 The Prometheus Authors
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at

Original file line number	Diff line number	Diff line change
`@@ -1,4 +1,4 @@`
`1`		`-// Copyright 2020 The Prometheus Authors`
	`1`	`+// Copyright 2018 The Prometheus Authors`
`2`	`2`	`// Licensed under the Apache License, Version 2.0 (the "License");`
`3`	`3`	`// you may not use this file except in compliance with the License.`
`4`	`4`	`// You may obtain a copy of the License at`