PowerVS: Remove unused function

When looking at regions, I found this old code.  Seeing as it is unused,
I removed it instead of updating it.

Author: hamzy

pkg/destroy/powervs/powervs.go

@@ -110,36 +110,6 @@ func fetchUserDetails(bxSession *bxsession.Session, generation int) (*User, erro
 	return &user, nil
 }
 
-// GetRegion converts from a zone into a region.
-func GetRegion(zone string) (region string, err error) {
-	err = nil
-	switch {
-	case strings.HasPrefix(zone, "dal"), strings.HasPrefix(zone, "us-south"):
-		region = "us-south"
-	case strings.HasPrefix(zone, "sao"):
-		region = "sao"
-	case strings.HasPrefix(zone, "us-east"):
-		region = "us-east"
-	case strings.HasPrefix(zone, "tor"):
-		region = "tor"
-	case strings.HasPrefix(zone, "eu-de-"):
-		region = "eu-de"
-	case strings.HasPrefix(zone, "lon"):
-		region = "lon"
-	case strings.HasPrefix(zone, "syd"):
-		region = "syd"
-	case strings.HasPrefix(zone, "tok"):
-		region = "tok"
-	case strings.HasPrefix(zone, "osa"):
-		region = "osa"
-	case strings.HasPrefix(zone, "mon"):
-		region = "mon"
-	default:
-		return "", fmt.Errorf("region not found for the zone: %s", zone)
-	}
-	return
-}
-
 // ClusterUninstaller holds the various options for the cluster we want to delete.
 type ClusterUninstaller struct {
 	APIKey         string