Remove unused rootlessSlirpSync fields from Container struct

The rootlessSlirpSyncR and rootlessSlirpSyncW fields were related to
slirp4netns support which has been removed. These unused fields were
causing golangci-lint validation failures.

Fixes validate job failures in CI.

Signed-off-by: Lokesh Mandvekar <[email protected]>

Author: lsm5

libpod/container.go

@@ -107,9 +107,6 @@ type Container struct {
 	runtime    *Runtime
 	ociRuntime OCIRuntime
 
-	rootlessSlirpSyncR *os.File
-	rootlessSlirpSyncW *os.File
-
 	rootlessPortSyncR *os.File
 	rootlessPortSyncW *os.File