Fix comment to match the arg name

Signed-off-by: Steven Burgess <steven.a.burgess@hotmail.com>

pkg/archive/archive.go

@@ -455,7 +455,7 @@ func TarWithOptions(srcPath string, options *TarOptions) (io.ReadCloser, error)
 }
 
 // Untar reads a stream of bytes from `archive`, parses it as a tar archive,
-// and unpacks it into the directory at `path`.
+// and unpacks it into the directory at `dest`.
 // The archive may be compressed with one of the following algorithms:
 //  identity (uncompressed), gzip, bzip2, xz.
 // FIXME: specify behavior when target path exists vs. doesn't exist.