[errors] Greatly simplify common/errors package.

common/errors/walk.go

Index: common/errors/walk.go
diff --git a/common/errors/walk.go b/common/errors/walk.go
index f313626bc80850be8689d41508c22523e767b031..5b80d26c448ecf47407c463570c2061dc38c1fb9 100644
--- a/common/errors/walk.go
+++ b/common/errors/walk.go
@@ -55,11 +55,3 @@ func Any(err error, fn func(error) bool) (any bool) {
 	})
 	return
 }
-
-// Contains performs a Walk traversal of an error, returning true if it is or
-// contains the supplied sentinel error.
-func Contains(err, sentinel error) bool {
-	return Any(err, func(err error) bool {
-		return err == sentinel
-	})
-}