fix: remove parentIsObject() check (#12851)

we will allow situations such as

```
a/b/1.txt
a/b
```

and

```
a/b
a/b/1.txt
```

we are going to document that this usecase is
not supported and we will never support it, if
any application does this users have to delete
the top level parent to make sure namespace is
accessible at lower level.

rest of the situations where the prefixes get
created across sets are supported as is.

cmd/erasure-healing.go

@@ -783,11 +783,9 @@ func (er erasureObjects) purgeObjectDangling(ctx context.Context, bucket, object
 		var err error
 		var returnNotFound bool
 		if !opts.DryRun && opts.Remove {
-			if versionID == "" {
-				err = er.deleteObject(ctx, bucket, object, writeQuorum)
-			} else {
-				err = er.deleteObjectVersion(ctx, bucket, object, writeQuorum, FileInfo{VersionID: versionID}, false)
-			}
+			err = er.deleteObjectVersion(ctx, bucket, object, writeQuorum, FileInfo{
+				VersionID: versionID,
+			}, false)
 
 			// If Delete was successful, make sure to return the appropriate error
 			// and heal result appropriate with delete's error messages