Use lib_free for the memory buffer allocated via strdup in net/procfs/net_procfs.c

[royfengsss]

Summary

In net/procfs/net_procfs.c the memory buffer of copy is allocated in strdup, which used lib_malloc.
It need to be freeed with lib_free
Otherwise, it will triger the assertion of "Free memory from the wrong heap" under flatmode and user seperated heap enabled case.

Impact

Fix a mismatch of malloc/free.

Testing

Pass the build, test with assertion enabled. no related assertion found anymore.

[xiaoxiang781216]

Don't need this patch after #10066, let's close it